China Biomass Cogeneration Development Project 56433 Fuel Supply Handbook for Biomass-Fired Power Projects China Biomass Cogeneration Development Project Fuel Supply Handbook for Biomass-Fired Power Projects Fuel Supply Handbook for Biomass-Fired Power Projects Prepared for World Bank/ESMAP Colophon BTG Biomass Technology Group BV P.O. Box 835 7500 AV Enschede The Netherlands Tel. +31-53-4861186 Fax +31-53-4861180 www.btgworld.com office@btgworld.com May 2010 Energy Sector Management Assistance Program (ESMAP) reports are published to communicate the results of ESMAP's work to the development community with the least possible delay. Some sources cited in this paper may be informal documents that are not readily available. The findings, interpretations, and conclusions expressed in this report are entirely those of the author(s) and should not be attributed in any manner to the World Bank, or its affiliated organizations, or to members of its board of executive directors for the countries they represent, or to ESMAP. The World Bank and ESMAP do not guarantee the accuracy of the data included in this publication and accepts no responsibility whatsoever for any consequence of their use. The boundaries, colors, denominations, other information shown on any map in this volume do not imply on the part of the World Bank Group any judgment on the legal status of any territory or the endorsement of acceptance of such boundaries. Contents Acknowledgments ................................................................................................................................................................................ vii Glossary ................................................................................................................................................................................................... viii Acronyms and Abbreviations................................................................................................................................................................x Executive Summary............................................................................................................................................................................... xii 1 Introduction ....................................................................................................................................................................................... 1 2 Biomass as a Source of Energy ......................................................................................................................................................2 2.1 . SourcesofBiomassFeedstock.............................................................................................................................................................................2 2.2 BiomassFeedstockCommonlyUsedinChina...............................................................................................................................................2 2.3 ThreeCategoriesofBiomassResidues..............................................................................................................................................................3 . 2.4 BiomassFuelCharacteristicsandFuelSelectionConsiderations..........................................................................................................3 2.4.1 BiomassConstituents.................................................................................................................................................................................4 2.4.2 ActualDensity,BulkDensity,andEnergyDensity..........................................................................................................................4 2.4.3 ParticleDimensionandParticleSizeDistribution..........................................................................................................................5 2.4.4 MoistureContent........................................................................................................................................................................................ 6 2.4.5 CalorificValue............................................................................................................................................................................................... 6 2.4.6 AshContentandQuality..........................................................................................................................................................................7 . 2.4.7 ChemicalComposition............................................................................................................................................................................. 8 2.4.8 Contaminants...............................................................................................................................................................................................10 E 2.5 xample:SomeExperienceswithBiomassFuel-FeedingSystems.......................................................................................................10 2.6 ConclusionsandRecommendations................................................................................................................................................................10 2.6.1 Conclusions...................................................................................................................................................................................................10 2.6.2 Recommendations...................................................................................................................................................................................... 11 3 Biomass Resource Assessment ................................................................................................................................................... 12 3.1 TypesofBiomassPotential................................................................................................................................................................................... 12 3.2 BasicApproachestoBiomassResourceAssessments.............................................................................................................................. 12 . 3.2.1 StatisticalAssessments............................................................................................................................................................................ 13 3.2.2 SpatiallyExplicitAssessments............................................................................................................................................................... 13 . 3.3 StepsinaBiomassResourceAssessment...................................................................................................................................................... 13 3.4 StrawResourceAssessmentsinChina............................................................................................................................................................. 14 iii Contents . 3.5 SpatiallyExplicitStrawResourceAssessments:AnExamplefromEurope...................................................................................... 15 3.5.1 StrawPotentialperRegion..................................................................................................................................................................... 15 3.5.2 StrawPotentialfor5x5kmGrids......................................................................................................................................................... 17 3.6 SizeoftheBiomassPowerPlant........................................................................................................................................................................18 3.7 ConclusionsandRecommendations................................................................................................................................................................18 3.7.1 Conclusions...................................................................................................................................................................................................18 3.7.2 Recommendations..................................................................................................................................................................................... 19 4 Biomass Supply from Straw ......................................................................................................................................................... 21 4.1 Introduction................................................................................................................................................................................................................ 21 4.2 TheTechnologyandMethodsofStrawProduction................................................................................................................................. 21 4.2.1 Production,Raking,andCollectionofStraw.................................................................................................................................. 21 4.2.2 TransportingStrawtoStorage............................................................................................................................................................. 22 4.2.3 Long-TermStorage.................................................................................................................................................................................... 22 . 4.2.4 DeliveryfromLong-TermStoragetoPowerPlant...................................................................................................................... 22 4.2.5 HandlingattheBiomassPowerPlant............................................................................................................................................... 23 4.3 CurrentStatusofStrawSupplyinChina....................................................................................................................................................... 24 4.3.1 StrawAvailabilityinChina...................................................................................................................................................................... 24 4.3.2 StrawCollectionPracticesinChina................................................................................................................................................... 24 4.4 StrawSupplyinChina:CaseStudies................................................................................................................................................................ 25 . CaseStudyA: 30MWBiomassPowerPlantinShandongProvince................................................................................................. 25 CaseStudyB: 12MWBiomassPowerPlantinHenanProvince.......................................................................................................... 26 CaseStudyC: 30MWBiomassPowerPlantinHenanProvince......................................................................................................... 26 CaseStudyD: 24MWBiomassPowerPlantinJiangsuProvince........................................................................................................ 26 4.5 StrawSupplyinEurope:CaseStudies............................................................................................................................................................. 26 . CaseStudyE: 39.7MWBiomass-FiredPowerPlantinEnsted,Denmark....................................................................................... 26 CaseStudyF: 38MWStraw-FiredPowerPlantinEly,UnitedKingdom......................................................................................... 26 CaseStudyG: 25MWStraw-FiredPowerPlantinSangüesa;Navarra,Spain................................................................................ 27 4.6 ConclusionsandRecommendations............................................................................................................................................................... 27 4.6.1 Conclusions.................................................................................................................................................................................................. 27 4.6.2 Recommendations....................................................................................................................................................................................28 5 Biomass Supply from Forestry Residues ................................................................................................................................. 29 5.1 Introduction............................................................................................................................................................................................................... 29 5.1.1 ForestryResiduesTypesandYields................................................................................................................................................... 29 5.1.2 ForestryResiduesProductionCostFactors.................................................................................................................................... 29 5.2 Harvesting(Extraction).......................................................................................................................................................................................... 30 5.2.1 ExtractioninConnectionwithFinalFelling.................................................................................................................................... 30 5.2.2 ExtractioninConnectionwithClearingandThinning................................................................................................................ 31 5.3 Comminution............................................................................................................................................................................................................. 31 . 5.3.1 ComminutionatLanding........................................................................................................................................................................ 31 5.3.2 ComminutionattheSource..................................................................................................................................................................33 5.3.3 ComminutionattheEnd-UseFacility............................................................................................................................................... 34 . 5.3.4 ComminutionataTerminal...................................................................................................................................................................37 iv Contents 5.4 BiomassFuelStorage...............................................................................................................................................................................................37 5.4.1 StoringForestryResiduesatRoadside..............................................................................................................................................37 5.4.2 StoringForestryResiduesatBiomass-FiredPowerPlant.......................................................................................................... 38 B 5.5 ioenergyFuelChainCaseStudiesfromChina.......................................................................................................................................... 38 5.6 BioenergyFuelChainCaseStudiesfromEurope....................................................................................................................................... 38 5.7 Conclusions................................................................................................................................................................................................................ 39 6 Managing the Biomass Fuel Supply .......................................................................................................................................... 42 6.1 OrganizingtheBiomassFuelSupply................................................................................................................................................................ 42 6.2 BiomassFuelContracting..................................................................................................................................................................................... 42 6.2.1 BiomassFuelQuantity..............................................................................................................................................................................43 6.2.2 BiomassFuelQuality.................................................................................................................................................................................43 . 6.2.3 BiomassFuelPricing................................................................................................................................................................................. 44 6.2.4 OtherSupplyContractConsiderations........................................................................................................................................... 44 6.3 BiomassFuelSupplyControl.............................................................................................................................................................................. 45 6.3.1 IntroductiontoFuelQualityControlMeasures........................................................................................................................... 45 . 6.3.2 QualityManagementforFuelSupplyControl.............................................................................................................................46 6.3.3 CaseStudy:QualityManagementofAgriculturalResiduesinDenmark........................................................................... 47 . 6.3.4 CaseStudy:QualityManagementofForestryResiduesinFinland..................................................................................... 47 M 6.4 itigationStrategiesforManagingSupplyRisks.......................................................................................................................................48 6.5 ConclusionsandRecommendations...............................................................................................................................................................49 References and Other Resources ...................................................................................................................................................... 51 Annexes 1 InternationalExperiencewithGrowingEnergyCrops........................................................................................................................................ 55 2 FuelStandardsandSpecifications...............................................................................................................................................................................58 3 . CalculationoftheNetCalorificValueatDifferentBasesandEnergyDensityasReceived--EN14961-1..................................... 61 4 TypesofBiomassPotential............................................................................................................................................................................................. 63 5 DeterminationofYieldfromAgriculturalCropsandResidues......................................................................................................................64 6 GuidelinesforPlanningaBiomassResourceSurvey............................................................................................................................................66 7 . FinnishResearchintoReducingBiomassSupplyCosts...................................................................................................................................... 67 8 . SampleBiomassFuelSupplyContract......................................................................................................................................................................68 9 EnergyDensityofForestChips..................................................................................................................................................................................... 77 10 AlternativesforReflectingEnergyContentinBiofuelPrice............................................................................................................................80 11 ExampleoftheSamplingandHandlingProcessforWoodFuels....................................................................................................................81 12 QualityManagementSystemforSolidBiomassSupply.................................................................................................................................... 82 13 FuelSupplyRiskMatrix.....................................................................................................................................................................................................84 v Contents Figures . 2.1 BiomassAppearancesandVolumes..............................................................................................................................................................................4 2.2 TheNetCalorificValue(NCV0=19MJ/kg)asaFunctionofWetDryBasisMoisture(Mandu)....................................................... 6 2.3 BottomAshStoredinaStorageTank(left),FlyAshIstheAshThatDerivesfromFlueGasCleaning(right)............................... 8 3.1 TheInfluenceofSustainabilityCriteriaonBiomassPotential......................................................................................................................... 13 . 3.2 StrawYieldasaFunctionofGrainYield................................................................................................................................................................... 16 3.3 TotalStrawProductionperRegion(tons)................................................................................................................................................................. 16 3.4 StrawUsedperHeadofCattle...................................................................................................................................................................................... 17 . 3.5 AvailableStrawperRegion(tons)................................................................................................................................................................................. 17 3.6 AvailableStrawper5x5kmGridCell(tons).............................................................................................................................................................. 17 4.1 TurningandRakingofSwathsBeforeBaling............................................................................................................................................................ 21 . 4.2 TractorandBalerinOperation...................................................................................................................................................................................... 21 4.3 LoadingStrawintheField............................................................................................................................................................................................... 22 4.4 OutdoorStorageofStraw.............................................................................................................................................................................................. 23 4.5 PoleBarninCaliforniaforStorageofRiceStraw.................................................................................................................................................. 23 . 4.6 TruckforLong-DistanceStrawTransport................................................................................................................................................................ 23 4.7 Unloading12BalesinOneOperation......................................................................................................................................................................... 23 5.1 TypicalCostStructureofForestChipsinFinland--PricesatPlant,ExcludingVAT,2002.................................................................... 30 5.2 ForestChipsProductionChainBasedonChippingatRoadside(Landing).................................................................................................32 5.3 ChipperTruck........................................................................................................................................................................................................................33 5.4 ForestChipsProductionChainBasedonTerrainChipping............................................................................................................................... 34 5.5 ForestChipsProductionChainBasedonComminutionofLooseResiduesatanEnd-UseFacility............................................... 35 5.6 Timberjack1490DResidueBaler................................................................................................................................................................................... 35 5.7 LoadingCRLBundlesonaForwarder......................................................................................................................................................................... 36 5.9 ProductionChainBasedonCompositeResidueLogs........................................................................................................................................ 36 5.8 StorageofCRLBundles.................................................................................................................................................................................................... 36 . 5.10 AWoodChipsDeliverySystemIntegratingDifferentSupplyConcepts................................................................................................... 39 5.11 AForestryResiduesSupplySystemBasedonBundledSlashDelivery........................................................................................................40 6.1 CostStructuresofDifferentForestryResiduesFuelsinFinland.................................................................................................................... 45 6.2 MethodologytoApplyandImplementQualityAssurance............................................................................................................................. 47 A2.1 CEN/TC335WithintheBiomass-Biofuel-BioenergyField................................................................................................................................58 A2.2 ExampleofClassificationBasedonOriginandSource,MajorTradedForm,andProperties............................................................ 59 A2.3 ExampleofaFuelQualityDeclarationUsedforBulkDelivery.......................................................................................................................60 A9.1 ExamplesoftheEnergyDensityofSelectedFuels,ShowingtheLoadVolumeRequiredfor1toe............................................... 78 . A12.1 DeterminationofCustomerRequirements............................................................................................................................................................ 82 Tables 2.1 SummaryofTypicalPropertiesofPrimary,Secondary,andTertiaryResidues...........................................................................................3 2.2 CompositionofDifferentBiomassTypes(percentageofweight,moisturefree).....................................................................................4 2.3 . BulkDensitiesofDifferentBiomassSources(indicativevalues).......................................................................................................................5 2.4 ethodologytoMeasuretheBulkDensityofForestChips..............................................................................................................................5 M 2.5 FuelDataatTypicallyOccurringMoistureContent...............................................................................................................................................7 2.6 GuidingValuesandGuidingRangesforElementsinBiomassAshesforUnproblematicThermalUtilization............................. 9 2.7 GuidingValuesandGuidingRangesforElementsinBiomassFuelsforUnproblematicThermalUtilization............................... 9 3.1 YieldofMainCropStrawsinChinaandTheirHeatingValues,2005............................................................................................................ 15 3.2 TypicalScaleofOperationforVariousSizesandTypesofBioenergyPlants............................................................................................ 19 5.1 ForestProductivityinFinland........................................................................................................................................................................................ 30 A9.1 TheEnergyDensityofForestBiomassChipsandCrushedBarkinFinlandat40PercentMoistureContent............................. 77 vi Acknowledgments This publication is part of a technical assistance activity Investment Consulting & Management Co. Ltd, led funded by the Energy Sector Management Assistance by Ding Hang with the participation of Jia Xiaoli, Li Program (ESMAP) for the promotion of biomass proj- Xiaozhen, and Wu Fan, prepared a background study ects in Inner Mongolia. This technical report was pre- report to analyze the current development status of pared with a view to identifying means for addressing the biomass power industry in China, and provided fuel supply problems faced by biomass projects, not valuable input to this fuel supply handbook. only in Inner Mongolia, but also in other provinces in China, as well as in many developing countries, where The World Bank team that supervised the consultants' fuel supply problems have, in many cases, delayed, or work and the preparation of the report consisted of even derailed, biomass projects. Ximing Peng, task team leader, and Noureddine Ber- rah, energy advisor. The team would like to give spe- This technical report was prepared by BTG Biomass cial recognition to peer reviewers Xiaodong Wang, Technology Group BV.1 The primary authors were Senior Energy Specialist at the World Bank; Shiping John Vos and Lud Uitdewilligen of BTG. The report Qin, Biomass Specialist at the Energy Research Insti- also benefited from the contributions of Eija Alakanga tute of the National Development Reform Commis- of the Technical Research Center of Finland (VTT), sion; and Huiyong Zhuang, Project Manager at the Patricia Thornley of the University of Manchester, and National Bio Energy Company of China. The team Alexandre Thébaud of BTG. Its dissemination is part would like to also thank Defne Gencer, Energy Ana- of the World Bank's efforts to share international expe- lyst at the World Bank, editor Rebecca Kary, editor riences in renewable energy and to ensure the success Sherrie Brown, graphic designer Gemma Drohm, and of biomass projects in developing countries. designer Laura Johnson for their efforts in producing the final publication. A team of experts from the China Energy Conser- vation Investment Corporation (CECIC) Blue-Sky The World Bank team also extends its gratitude to Ede Ijjasz, Sector Manager at the World Bank's China and Mongolia Sustainable Development Unit, and 1. BTG Biomass Technology Group BV is a Dutch firm of bio- Amarquaye Armar, Manager, ESMAP, who provided mass specialists. For more than 20 years, BTG has specialized in the process of conversion of biomass into useful fuels and the resources and guidance to make this publication energy. possible. The financial and technical support by the Energy Sector Management Assistance Program (ESMAP) is gratefully acknowledged. ESMAP--a global knowledge and technical assistance partnership administered by the World Bank and sponsored by official bilateral donors--assists low- and middle-income countries, its "clients," to provide modern energy services for poverty reduction and environmentally sustainable economic development. ESMAP is governed and funded by a Consultative Group (CG) comprised of official bilateral donors and mul- tilateral institutions, representing Australia, Austria, Canada, Denmark, Finland, France, Germany, Iceland, the Netherlands, Norway, Sweden, the United Kingdom, and the World Bank Group. vii Glossary Agricultural residues: Byproducts of agricultural prac- Calorific value, heating value: Energy amount per unit tice (cultivation of farms and harvesting activities), mass or volume released on complete combustion. labeled as "primary" and byproducts of the process- ing of agricultural products, for example, for food Density: Ratio of mass to volume. It must always be or feed production, labeled as "secondary." Straw of stated whether the density refers to the density of wheat and corn are examples of primary agricultural individual particles or to the bulk density of the mate- residues. Bagasse and rice husks are examples of sec- rial and whether the mass of water in the material is ondary agricultural residues. included. Bioenergy: All types of energy derived from biofuels, Dry basis: Condition in which the solid biofuel is free including wood energy and agro-energy. from moisture. Biofuel: Any solid, liquid, or gaseous fuel produced Dry matter: Material after removal of moisture under from biomass. specific conditions. Biomass: The organic matter generated by the photo- Energy crops: Plants grown to produce biofuels, or synthesis of plants. The source of biomass will depend directly exploited for their energy content. Commer- to some extent upon the availability in the local area. cial energy crops are typically densely planted, high- Basically, five categories of raw materials are used for yielding crop species, such as Miscanthus, Salix L., or biomass fuel production: forestry residues, energy Populus L. crops, agricultural residues, food waste, and industrial waste and coproducts. Feedstock: Any biomass destined for conversion to energy or biofuel. For example, corn is a feedstock Biomass-fired power generation: Biomass is burned in for ethanol production, and soybean oil is a feedstock specially designed boilers to generate high-pressure for biodiesel. Cellulosic biomass has the potential to steam to drive the turbine and transfer the power to become a significant feedstock source for biofuels. the generator for electricity generation. Forestry residues: Both primary residues, that is, left- Biomass resource assessment: An assessment to deter- overs from cultivation and harvesting activities (such mine the availability of biomass for a power plant. as twigs, branches, and precommercial thinning mate- The type of potential is a crucial criterion when dis- rial) and secondary residues, that is, those resulting cussing biomass availability because it determines from any processing steps (such as sawdust, bark, and the approach and methodology and thereby the data black liquor). requirements of the biomass resource assessment. Fossil fuel: A nonrenewable energy source produced by Bulk density: Mass of a portion of a solid fuel divided the remains of living organisms that built up under- by the volume of the container that is filled by that ground over geological periods in liquid (oil), solid portion under specific conditions. (coal, peat), and gaseous (natural gas) forms. viii Glossary Gray straw: Straw that has been lying in the field and Sawdust: Fine particles created when sawing wood. that has been exposed to rain has a reduced content of the corrosive matter, chlorine and potassium. Contrary Straw: Straw is an agricultural byproduct, the dry to "yellow" straw, this "gray" straw is less wearing on part of a cereal plant, after the grain or seed has been the boiler, since part of the matter that corrodes the removed. boiler wall and tubes has been removed. Gray straw also has a somewhat higher calorific value than yellow Quality management system: A tool to control the over- straw. all supply chain to ensure fuel quality. Organic matter: Combustible fraction of dry matter. Volume: Amount of space that is enclosed within an object. Particle size distribution: Proportion of various particle sizes in a solid fuel. Wet basis: Condition in which the solid biofuel con- tains moisture. Renewable energy: Energy produced from sources that can be renewed indefinitely, for example, hydro, solar, Wood chips: Chipped woody biomass in the form geothermal, and wind power, as well as sustainably of pieces with a defined particle size produced by produced biomass. mechanical treatment with sharp tools, such as knives. Wood chips have a subrectangular shape with a typi- Roundwood: Wood in its natural state as felled, with cal length of 5­50 mm and a low thickness compared or without bark. with other dimensions. ix Acronyms and Abbreviations BEE Biomass Energy Europe HHV Higher heating value C Carbon K Potassium Ca Calcium LHV Lower heating value CCP Critical control point MC Moisture content Cd Cadmium N Nitrogen CEN European Committee for NCV Net calorific value (same as LHV) Standardization NOx Nitrogen oxides CEN/TC European Committee for NUTS Nomenclature of Territorial Units Standardization/Technical Committee for Statistics, a geocode standard for CHP Combined heat and power referencing the administrative divisions of countries for statistical purposes Cl Chlorine (nomenclature d'unités territoriales CRESP China Renewable Energy Scale-Up statistiques) Program O Oxygen CRI Crop residue index odt Oven dry ton CRL Composite residue log OECD Organisation for Economic Co- d.b. Dry basis operation and Development DIN German Standardization Institute ONORM Austrian Standardization Institute (Deutsches Institut für Normung) (Österreichisches Normungsinstitut) ESMAP Energy Sector Management Assistance QA Quality assurance Program QM Quality management EU European Union RE Renewable energy Eurostat Statistical office of the European Union RF Recoverability factor GCV Gross calorific value (same as HHV) RPF Residue-to-product factor GIS Geographical Information System S Sulfur H Hydrogen SOx Sulfur oxides HCL Hydrochloric acid SRWC Short-rotation woody crops x Acronyms and Abbreivations UK United Kingdom kWh Kilowatt-hour VTT Technical Research Centre of Finland m Meter (Valtion Teknillinen Tutkimuskeskus) m2 Square meter w.b. Wet basis m3 Cubic meter wt% on d.b. Weight percent MJ Megajoule Zn Zinc mu Chinese unit of area (1 ha = 15 mu) MW Megawatt UNITS OF MEASURE MWe Megawatt electric cm Centimeter MWh Megawatt-hour GJ Gigajoule MWth Megawatt thermal GW Gigawatt MWh/m3 Megawatt-hours per cubic meter GWh Gigawatt-hour t Ton (metric) ha Hectare tce Ton of coal equivalent hr Hour toe Ton of oil equivalent kg Kilogram TWh/a Terawatt-hours per year km Kilometer yr Year km2 Square kilometer kWth Kilowatt-thermal xi Executive Summary Biomass energy development in China is supported by and/or validate biomass resource data. It is impor- the Energy Sector Management Assistance Program tant to use a consistent biomass resource assessment (ESMAP) project entitled China Biomass Cogenera- methodology that not only applies theoretical crop- tion Development, Heating Network Development. to-residue factors, but also considers the competitive Biomass Technology Group BV (BTG) was commis- uses of biomass, and material losses incurred during sioned by ESMAP to write an operation-oriented biomass collection, storage, and transport caused by handbook to provide new investors in the sector with climate, humidity, and other reasons. Furthermore, guidance on managing their fuel supply risk during the it is always necessary to involve an experienced pro- planning and preparation stage of bioenergy projects. fessional (consultant organization) to support the The handbook is divided into five chapters following resource assessment. the Introduction. Biomass Supply from Straw Biomass as a Source of Energy In the preparation stage of a bioenergy project, a The characteristics of the biomass used as fuel have a good understanding and organization of the biomass direct impact using biomass power plant design, oper- supply chain are necessary to realize an optimal fuel ation, and performance. They also have an impact on supply to the power plant. When using straw for the best way to handle fuel (for example, collection, energy purposes, the supply chain logistical principles transport, pretreatment, and storage). Less homoge- are basically no different than for traditional straw neous and/or low-quality fuels need more sophisti- applications. However, the scale of operation is sig- cated combustion systems. Similarly, appropriate fuel nificantly larger, calling for some degree of mecha- selection is vital in managing fuel supply risk. Fuel nization and automation. The challenge for Chinese standards and specifications have been developed to straw suppliers is to organize the highest throughput support the matching of fuel supply and energy sys- in straw collection at the lowest cost. Important les- tem. A plant design and environmental permits that sons can be learned from Denmark, where practical allow as much fuel flexibility as possible are recom- experience operating biomass power and combined mended in anticipation of possible changes in biomass heat and power (CHP) plants using wheat straw has fuel supply. been gained since the late 1980s. However, because of different local circumstances in China, the Danish experience cannot be copied directly. Biomass Resource Assessment During the planning stage of the biomass-fired power Biomass Supply from Forestry Residues plant project, a biomass resource assessment is required to determine the biomass availability in the selected For optimal management of fuel supply to the bio- area. It is better not to rely exclusively on any prior mass-fired power plant, a good understanding and biomass resource assessment, if and where available, organization of the biomass supply chain is required. but to carry out a dedicated survey to collect, verify, When using forestry residues for energy production, xii Executive Summary it is crucial to consider harvesting (extraction), com- Managing the Biomass Fuel Supply minution (chipping or crushing), transportation, and storage costs carefully. The selection of the forest fuel The aim of biomass contracting is to secure the long- harvesting technology requires complex technical term availability of biomass fuel for the right price; analysis, taking into account the annual need for for- therefore, long-term contracts are preferred. At the est fuels and other fuels, annual availability of forest plant planning stage, biomass should be contracted for fuels, location of plant, size of plant yard, type of bio- before the biomass-fired power plant goes onstream, mass energy plant, prevailing technology to produce to have sufficient biomass fuel readily available before chips, and the need for Geographical Information Sys- initial operation. tem­ (GIS-) based availability and cost analysis. At the plant operational stage, it is important to The production methods and cost breakdown for for- ensure that biomass fuel delivered to the biomass est chips vary considerably between countries and power plant meets the contractual fuel standards and regions. Generally, the cost depends on how well the specifications. Biomass fuel not in compliance with unit operations in the supply chain are organized and the contractual standards and specifications can cause structured. Furthermore, the efficiency of a procure- operational problems with the combustion process, or ment system is highly dependent on the environment can decrease the equipment life span. Fuel quality con- and infrastructure in which it operates. Economic, trol is necessary throughout the whole supply chain, social, ecological, industrial, and educational factors, and it is recommended that investors apply some kind as well as local traditions, also have effects. Conse- of quality management (QM) system. It is important quently, there is no single production system that can to write practical procedures into a manual that can be seen as the optimal solution for all countries, or for serve as a tool for each unit operation in the biomass all situations within a given country. supply chain, such that all the processes and interac- tions are fully under control. Finally, an instrument for assessing fuel supply risks and developing mitiga- tion strategies is described. xiii 1. Introduction This handbook provides an overview of the main top- included to give prospective Chinese investors a sense ics that need consideration when managing the sup- of the type of organization required, the levels of pro- ply of biomass to large biomass power plants. It will ductivity achievable, and the current technological help investors in China to develop, with assistance of state of the art, so as to appreciate better the possi- local biomass supply experts, their own solutions. The bilities and challenges of arranging large-scale, highly focus is on biomass residues, in particular agricultural mechanized biomass supplies. Solutions developed residues (mainly straw and stalks) and forestry resi- and applied in Scandinavia cannot be copied one-to- dues (mainly residues from forestry operations). one in China, but the approach, technology, and logis- tics developed elsewhere in the world can give Chinese The handbook is intended to provide the reader a com- investors insight into and inspiration for setting up prehensive overview of the relevant issues to consider and optimizing biomass supply chains in China. when planning and preparing an investment in a bio- mass power plant. Each chapter covers (a) a thorough This handbook covers a wide range of topics related introduction of the relevant topics; (b) best practices to biomass fuel supply risk in the planning and prepa- and case studies from China and from leading over- ration stages for a biomass-fired power plant. chapter seas countries, showcasing international experience; 2 introduces the use of biomass as an energy source, and (c) lessons learned, practical tips, and sugges- including fuel selection considerations and the fuel tions for candidate investors in biomass energy plants. standards and specifications required to match a par- In particular, the report describes the experience of ticular fuel supply to a power generation system. chap- Scandinavian countries as an illustration of best prac- ter 3 describes the use of biomass resource assessments tices. Denmark is a world leader in large-scale energy at the project planning stage. chapters 4 and 5 give production from straw, and Finland and Sweden are insight into the biomass supply from straw and for- world leaders in large-scale energy production from estry residues, respectively. Fuel supply management forestry residues. is covered in chapter 6, which addresses the topics to be considered both at the plant planning stage and at With regard to biomass supply, each biomass power the operational stage. It describes a methodological plant needs its own solution based on local conditions approach for fuel inspection and quality control, as and circumstances and, unlike in China, Scandinavia well as an instrument for assessing fuel supply risks biomass production is highly mechanized. The expe- and developing mitigation strategies. rience gained in Denmark, Finland, and Sweden is 1 2. Biomass as a Source of Energy This chapter introduces different categories of raw animal bedding, such as poultry litter; and organic material that can be used as biomass feedstock (sec- material from excess production or insufficient tion 2.1), explains why this handbook will focus on market, such as grass silage. the use of biomass residues as feedstock (section 2.2), · Food waste comes from food and drink manufac- and presents a classification of biomass residues (sec- ture, preparation, and processing, and includes tion 2.3). post-consumer waste. Along the entire food sup- ply chain, huge quantities of waste are produced Those topics are followed by a description of the that are distinguishable as wet and dry waste. The most important fuel characteristics of agricultural majority consists of waste that has relatively high and forestry biomass residues, and a discussion of the moisture content. relevance of these characteristics for the design, opera- · Industrial waste and coproducts result from manu- tion, and performance of biomass-fired power plants facturing and industrial processes. During many (section 2.4). Finally, some examples of operational industrial processes, residues, waste, or coproducts experience with biomass fuel-feeding systems in North are produced that are further divided into woody America are presented (section 2.5). and nonwoody materials (such as paper pulp and wastes, textiles, or sewage sludge). 2.1 Sources of Biomass Feedstock 2.2 Biomass Feedstock Commonly A wide variety of raw materials can be used to produce Used in China biomass fuels. The source of biomass will depend to some extent on the availability in the local area. Basi- In China, all the above-mentioned raw material cate- cally, five categories of raw materials are used for bio- gories are available, in principle, for power generation mass fuel production (Biomass Energy Centre 2009). and eligible for support under the Renewable Energy (RE) Law that entered into force on January 1, 2006. · Forestry residues result from forestry, cultivation In practice, much of the power generation capacity and management of trees, or from wood processing expansion since has been based on agricultural resi- activities. Wood fuel can be derived from conven- dues, that is, maize stalks, cotton stalks, wheat straw, tional forestry practice and from tree management rice stalks, and husks. A few projects also use forestry operations and the management of parks, gardens, wastes, such as branches of fruit trees, tree bark, roots and transport corridors. of fast-growing poplar, shrub stumps, and wood-pro- · Energy crops are high-yield crops grown specifi- cessing wastes. The fuel used would seem to depend cally for energy applications. Energy crops can mainly on what biomass is available in sufficient be categorized into short-rotation energy crops, quantities and at an affordable price. Although energy grasses and agricultural energy crops, and aquatics crops offer substantial potential, in particular in the (hydroponics). medium to long term, the biomass quantities required · Agricultural residues are derived from agriculture and the current level of financial support available harvesting or processing. Agricultural residues can under the RE law for biomass-based power generation be further differentiated into the arable crop resi- is insufficient to render energy crop­based power gen- dues of straw or husk; animal manures and slurries; eration economic. Generally speaking, the cultivation 2 Biomass as a Source of Energy of dedicated energy crops will only be a viable option the processing of agricultural products, for example, for large-scale biomass production in the long term.2 for food or feed production, labeled as "secondary." For this reason, this handbook focuses on the biomass Straw from wheat and corn are examples of primary categories most widely used in the recently estab- agricultural residues. Bagasse and rice husks are exam- lished Chinese biomass-fired power plants: biomass ples of secondary agricultural residues. residues. Forestry biomass refers to harvests from forests avail- able for wood supply. Forestry residues include both 2.3 Three Categories of Biomass Residues primary residues, that is, leftovers from cultivation Biomass residues can be divided into primary, second- and harvesting activities (such as twigs, branches, and ary, and tertiary residues, released after harvest, dur- precommercial thinning material), and secondary resi- ing processing, or after end use, respectively.3 Table dues, that is, those resulting from any processing steps 2.1 sketches typical characteristics of the various resi- (for example, sawdust, bark, and black liquor). due categories. 2.4 Biomass Fuel Characteristics and Agricultural residues are the byproducts of agricul- Fuel Selection Considerations tural practice (cultivation of farms and harvesting activities), labeled as "primary," and byproducts of Because of the wide variety of raw materials, there is also considerable variation in fuel characteristics, even 2. Annex 1 discusses international experience with growing dif- when limiting the assessment to forestry and agricul- ferent types of energy crops for solid biomass production. tural residues. This section explores the main biomass 3. Until 2006, most of the biomass-fired generation capacity fuel characteristics, such as biomass constituents, bulk installed in China was based on secondary residues, in particu- lar on bagasse, the fibrous residue that remains after sugarcane and energy density, particle dimension and particle or sorghum stalks are crushed to extract their juice. Second- size distribution, moisture content, calorific value, ary residues are generally the most attractive feedstock for ash content and quality, chemical composition, and bioenergy production because they are released centrally and contaminants. are relatively clean. Primary residues are the best alternative. Although collection costs are higher, their availability is gener- ally substantial. Table 2.1 Summary of Typical Properties of Primary, Secondary, and Tertiary Residues Characteristic Primary residues Secondary residues Tertiary residues Origin Harvest residues Processing residues Residues after end use Typical examples Stalks, straw, thinnings Bagasse, husks, sawdust Demolition wood, organic waste Release During harvest season Part of the year, or Throughout the year throughout the year Accessibility Distributed on land, during High, typically released centrally Centrally at waste collection site, harvest in factory, during processing after end use Collection costs High Low Low to moderate Contamination Possibly sand, which can Generally low Depends on use, increased risk of lead to high ash content foreign materials (other waste materials) Alternative uses Mainly soil fertilization and Cattle feed, factory energy Incineration with energy recovery cattle feed and bedding demand Source: BTG. 3 Fuel Supply Handbook for Biomass-Fired Power Projects Table 2.2 Composition of Different Biomass Types (percentage of weight, moisture free) Biomass type Cellulose Hemi-cellulose Lignin Extractives Ash Softwood 41 24 28 2 0.4 Hardwood 39 35 20 3 0.3 Pine bark 34 16 34 14 2 Straw (wheat) 40 28 17 11 7 Rice husks 30 25 12 18 16 Peat 10 32 44 11 6 Source: Wagenaar, Prins, and Swaaij 1994. These biomass fuel characteristics are relevant for the Hemi-cellulose molecules are polymers built of about design, operation, and performance of the biomass- 200 C5- and C6- sugars with a much smaller degree of fired power plant. It is also important to take into polymerization, embedded in the cell walls of plants. account that the availability of a biomass fuel may Lignin, with an empirical formula of approximately change over time (as other opportunities arise or origi- CH1.5O0.6 , is a three-dimensional polymer composed nal fuel sources dry up). Appropriate fuel selection is of phenolic units. It serves as the "glue" between indi- an important aspect of managing fuel supply risks (see vidual cells. Table 2.2 presents the composition of dif- chapter 6). ferent types of biomass. Wiltsee (2000) argues that selecting a power plant 2.4.2 Actual Density, Bulk Density, and Energy Density design and applying for permits that allow maximum The actual density of different sources of biomass flexibility in the use of feedstock are the best strategy does not vary much. There is, however, a large range to deal with a potential change in fuel mix. of different shapes and sizes of biomass (for exam- ple, wood is available as roundwood, stacked logs, 2.4.1 Biomass Constituents chopped logs, or forest chips), as can be seen in figure At the molecular level, biomass consists of three mole- 2.1, which influences biomass weight in relation to cule types: cellulose, hemi-cellulose, and lignin. Cellu- volume. Therefore, it is better to talk about the bio- lose is the structural component of the primary cell wall mass bulk density. Table 2.3 shows bulk densities for of green plants. Cellulose is a straight, stiff molecule straw, wood, and coal. consisting of several thousands of glucose (C6-) units. Figure 2.1 Biomass Appearances and Volumes Source: Francescato and others 2008. 4 Biomass as a Source of Energy Table 2.3 Bulk Densities of Different Biomass Table 2.4 Methodology to Measure the Bulk Sources (indicative values) Density of Forest Chips Biomass shape Bulk density (kg/m3) 1. Use a bucket of known volume (e.g., 13 liters) and a Straw (chopped) 50 pair of scales. Straw (big bales) 130 2. Take a representative sample from the truck Straw pellets 600 container, e.g., 3 buckets from a 40 m3 container (ref. CEN/TS 14778-1), and fill the bucket without Wood chips 250 compacting the chips. Sawdust 200 3. Weigh the samples and divide their mean value (kg) Wood pellets 650 by the known volume (liters); e.g., Coal 850 (3.25 kg x 1,000 liters) 4 13 liters = 250 kg per measurement. Source: Francescato and others 2008. Source: Francescato and others 2008. Because biomass has a lower bulk density and a lower energy density than coal or natural gas, larger quanti- ties are required to produce the same electrical output, and the boiler design needs to be different. Energy den- sity, the result of dividing the bulk density by the net calorific value, influences the fuel logistics (transport and storage), the fuel-feeding system, and the process control of the thermal conversion process (van Loo and Koppejan 2002). When the biomass-fired power plant is to run on a biomass fuel with a low bulk den- sity, densification of the raw material may be neces- sary, depending on the transport distance between the collection area for the raw material and the power plant. A methodology to measure the bulk density of forest chips through sampling is described in table 2.4. feeding systems are capable of handling fuels with a 2.4.3 Particle Dimension and Particle Size Distribution broad range of particle sizes (such as walking floors and Depending on the supply chain, biomass fuels arrive "ram stokers"), whereas others tolerate only a narrow at the power plant as unit or bulk material. For agri- range of particle sizes (for example, pellet burners). The cultural residues such as straw, the material is usually variation in particle size, or particle size distribution, delivered in bales (unit material). Wood is often deliv- can be homogeneous (for example, pellets) or nonho- ered chipped or pelletized (bulk material). The parti- mogeneous (for example, untreated bark). cle dimension and particle size distribution need to be carefully matched with the applicable (a) fuel-feeding Depending on the type, size, shape, and quality of the system and (b) combustion technology. biomass fuel, different combustion technologies are applied. Less homogeneous and lower-quality fuels Biomass feeding systems impose limitations on the size need more sophisticated combustion systems. Low- and shape of feedstock. For example, oversized fuel quality biomass can only be combusted properly in particles can jam certain fuel-feeding systems. Some medium- and large-scale systems. 5 Fuel Supply Handbook for Biomass-Fired Power Projects Fuel standards have been introduced for biomass to Figure 2.2 The Net Calorific Value (NCV0 = 19 MJ/kg) become a commodity fuel with common definitions, as a Function of Wet Dry Basis Moisture common methods, and a clear classification system. (M and u) In Europe, the European Committee for Standardiza- tion (CEN) established a technical committee (CEN/ moisture on d.b. (u%) TC 335) to develop standards to describe all forms 0 25 67 150 400 40 of solid biomass, including wood chips, wood pellets 35 calorific value (MJ/kg) and briquettes, logs, sawdust, and straw bales. The 30 CEN/TC 335 standards support the matching of the 25 thermal conversion system with the fuel supply. More 20 information on fuel standards and specifications is 15 presented in annex 2. 10 5 2.4.4 Moisture Content 0 An important biomass characteristic influencing com- 0 10 20 30 40 50 60 70 80 bustion behavior, the adiabatic temperature of com- moisture on w.b. (M%) bustion, and the volume of flue gas produced per energy unit is the moisture content (water content). Source: Francescato and others 2008. Fuels with higher moisture content will have a greater mass and, therefore, higher bulk densities. With a released, the calorific value is expressed either as gross higher moisture content, the energy density will be calorific value (GCV) or net calorific value (NCV).4 In lower, and the subsequent volume of fuel required for the first case, the water is released as a liquid; in the a given amount of heat will be larger. The moisture second case, the water is released as a vapor, and the content of biomass fuel depends on such factors as the thermal energy required for vaporization is deducted. kind of material, the time of harvesting, the kind of When not explicitly specified in the literature, calorific pretreatment, and the method and duration of storage value is generally assumed to be NCV. (van Loo and Koppejan 2002). The moisture content for straw varies between 10 and 25 percent. Wood For thermal conversion, a biomass fuel with low mois- from the forest has a moisture content that may vary ture content is preferred because its calorific value is from 15 to 60 percent, depending on the duration of higher. In figure 2.2, the effect of moisture content open-air seasoning (Francescato and others 2008). on calorific value (NCV) is shown for wood. In table 2.5, calorific value is shown for straw, wood, coal, For optimal operation of the biomass boiler, keeping and natural gas. According to van Loo and Koppe- the moisture content as constant as possible is impor- jan (2008), the GCV of biomass fuels usually varies tant. Firing a fuel with a higher moisture content between 18 and 22 MJ/kg dry basis (d.b.) and can than the design value can result in lower conversion be calculated reasonably well by using the following efficiency, lower power output, and higher levels of empirical formula: harmful emissions (van Loo and Koppejan 2002). In practice, this means that most often only one type of GCV = 0.3491 × XC + 1.1783 × XH + 0.1005 × XS ­ 0.0151 × biomass is used per boiler. Another possibility is to XN ­ 0.1034 × XO ­ 0.0211 × Xash [MJ/kg, d.b.], blend fuels into a homogeneous mixture or integrate a drying step into the biomass supply chain. where Xi is the content of carbon (C), hydrogen (H), sulfur (S), nitrogen (N), oxygen (O), and ash in wt% 2.4.5 Calorific Value (d.b.). A bomb calorimeter can be used for exact The calorific value refers to the heating potential of a fuel and is a measure of its energy content (MJ/kg). 4. Sometimes also referred to as higher heating value (HHV) Depending on how water in the combustion products is and lower heating value (LHV), respectively. 6 Biomass as a Source of Energy Table 2.5 Fuel Data at Typically Occurring Moisture Content Unit Yellow strawa Gray strawa Wood chips Hard coal Natural gas Moisture content % 10­20 10­20 40 12 0 Volatile components % > 70 > 70 > 70 25 100 Ash % 4 3 0.6­1.5 12 0 Carbon (C) % 42 43 50 59 75 Hydrogen (H) % 5 5.2 6 3.5 24 Oxygen (O) % 37 38 43 7.3 0.9 Chloride (Cl) % 0.75 0.2 0.02 0.08 -- Nitrogen (N) % 0.35 0.41 0.3 1 0.9 Sulfur (S) % 0.16 0.13 0.05 0.8 0 Calorific value, water and ash-free MJ/kg 18.2 18.7 19.4 32 48 Calorific value, actual MJ/kg 14.4 15 10.4 25 48 Ash softening temperature °C 800­1,000 950­1,100 1,000­1,400 1,100­1,400 -- Source: Nikolaisen and others 1998. Note: -- = Not applicable. a. Straw that has been lying in the field and that has been exposed to rain has less corrosive matter, chlorine and potassium. Contrary to "yellow" straw, this "gray" straw is less wearing on the boiler because part of the matter that corrodes the boiler wall and tubes has been removed. Gray straw also has a somewhat higher calorific value than yellow straw (Nikolaisen and others 1998). determination of the GCV according to standardized calculate the NCV at dry base and as received. Details procedures. As van Loo and Koppejan (2008) men- on the standard are provided in annex 3. tion, the content of C, H, and S contributes positively to the GCV, while N, O, and ash contribute negatively Drying biomass fuel increases its calorific value. to the GCV. 2.4.6 Ash Content and Quality The NCV can be calculated from the GCV, taking into After the thermal conversion of biomass, bottom account the moisture and hydrogen content of the fuel ashes, fly ashes, and/or slags remain, depending on by applying the following equation: the fuel and technology used. Bottom ash is taken out at the bottom of the boiler (stored in a storage w w h NCV = GCV 1 ­ ­ 2,444 × ­ 2,444 × × 8.936 tank; see left panel of figure 2.3), and the remainder 100 100 100 w is whirled round in the boiler with the combustion air 1­ [MJ/kg, w.b.], 100 and removed by a flue gas cleaning system (fly ash; see right panel of figure 2.3). Fly ash can further be where w is the moisture content of the fuel in wt% divided into cyclone light ash and fine particles from (w.b.), h is the concentration of hydrogen in wt% (d.b.), electrostatic and bag filters. Storage and sale can be 2.444 is the enthalpy difference between gaseous and considered as treatment options for the collected liquid water at 25°C and 8.936 is MH2O/MH2; that is, ashes. Ashes are often recycled and used as a constitu- the molecular mass ratio between H2O and H2. ent of construction materials. The European Standard EN 14961:2005 Solid Biofu- The amount and quality of ash are important char- els--Fuel Specifications and Classes normalizes how to acteristics when selecting a biomass fuel. Both are 7 Fuel Supply Handbook for Biomass-Fired Power Projects Figure 2.3 Bottom Ash Stored in a Storage Tank (left), Fly Ash Is the Ash That Derives from Flue Gas Cleaning (right) Source: Francescato and others 2008. dependent on the biomass fuel that is used. Accord- For a wide range of biomass feedstocks, chemical and ing to Francescato and others (2008), debarked wood physical characteristics are included in the Phyllis is the lowest ash-containing biomass, whereas agri- database, accessible at www.ecn.nl/phyllis. cultural residues typically have a high ash content. The ash content of debarked wood is usually less than The presence of these salts, minerals, and other ele- 1 percent, while the ash content of agricultural resi- ments partly determine the level of gaseous and par- dues is 5­10 percent--and as much as 20 percent for ticulate emissions, ash, and slagging. Some guiding rice husk. values and guiding ranges for elements in biomass are shown in table 2.7, including the problems that can Besides the quantity of ash, the chemical composition occur and selected techniques to reduce the values to of ash is important because it can influence the melt- within the guiding ranges. ing behavior. Because the ash melting point of straw is lower than the ash melting point of wood, slag can be Biomass fuel characteristics, such as the area of origin, produced. According to Nikolaisen and others (1998), ash content, chemical content, and to some extent, this is important, particularly for power plants where a moisture content, affect the level and composition high steam temperature is desired to achieve great effi- of emissions into the air. When maintaining the local ciency. In table 2.6, some guiding values and guiding air quality is a crucial consideration in the planning, ranges for elements in biomass ashes are shown, includ- consent, and permitting processes, emissions have ing the problems that can occur and some techniques direct implications for the suitability of biomass fuel. to reduce the values to within the guiding ranges. In Europe, ever-stricter levels for the emissions of nitrogen oxides (thermal NOx and fuel NOx) are set 2.4.7 Chemical Composition because of their harmful effects on the environment. Biomass contains low levels of minerals, salts, and To meet the NOx emission level values, it is important other materials taken up from the soil or air dur- to work with temperatures as low as possible and with ing growth. Table 2.7 shows some fuel data and the accurate control of the combustion air (Vos 2005a). chemical composition of wheat straw, wood, coal, and Furthermore, it is important to consider the use of natural gas. According to Pastre (2002), the higher emissions-reduction equipment. concentrations of the elements nitrogen (N), sulfur (S), and chlorine (Cl) in straw are a result of the use of When using straw, which has a relatively high potas- pesticides and fertilizer. sium content, fuel slagging can be a serious problem. 8 Biomass as a Source of Energy Table 2.6 Guiding Values and Guiding Ranges for Elements in Biomass Ashes for Unproblematic Thermal Utilization Elements that can cause Guiding concentration problems outside of guiding Techniques for reduction Element in the ash (wt% on d.b.) Limiting parameter concentration ranges to guiding ranges Ca 15­35 Ash-melting point Straw, cereals, grass Temperature control on the grate and in the furnace K < 7.0 Ash-melting point, Straw, cereals, grass To prevent corrosion: deposits, corrosion see Cl (table 2.7) -- Aerosol formation Straw, cereals, grass Efficient dust precipitation, fuel leaching Zn < 0.08 Ash recycling Bark, wood chips, sawdust Fractioned heavy-metal separation -- Particulate emissions Bark, wood chips, sawdust Efficient dust precipitation, treatment of condensates Cd < 0.0005 Ash recycling Bark, wood chips, sawdust See Zn -- Particulate emissions Bark, wood chips, sawdust See Zn Source: van Loo and Koppejan 2002. Note: d.b. = dry basis. Guiding values for ashes related to the biomass fuel ashes according to ISO 1171-1981 at 550°C; analytical method recommended for ash analysis: pressurized acid digestion and inductively coupled plasma mass spectrometry (ICP) or flame atomic absorption spectrometry (AAS) detection. Table 2.7 Guiding Values and Guiding Ranges for Elements in Biomass Fuels for Unproblematic Thermal Utilization Guiding concentration Outside guiding in the fuel concentration ranges, Techniques for reducing to within Element (wt% on d.b.) Limiting parameter problems can occur for guiding ranges N < 0.6 NOx emissions Straw, cereals, grass Primary measures (air staging, reduction zone) < 2.5 Waste wood, fiber boards Secondary measures (SNCR or SCR process) Cl < 0.1 Corrosion Straw, cereals, grass · Fuelleaching · Automatic heat exchanger cleaning · Coating of boiler tubes · Appropriate material selection < 0.1 HCL emissions Straw, cereals, grass · Dry sorption · Scrubbers · Fuel leaching < 0.3 PCDD/F emissions Straw, cereals, grass · Sorption with active carbon · Catalytic converters S < 0.1 Corrosion Straw, cereals, grass See Cl < 0.2 SOx emissions Grass, hay See HCL emissions Source: van Loo and Koppejan 2002. Note: d.b. = dry basis; SNCR = Selective non-catalytic reduction; SCR = Selective catalytic reduction; PCCD/F = Emissions of polychlorinated dibenzodioxin and dibenzofuran. N and S analysis recommended: combustion/gas chromatographic detection; Cl analysis recommended: bomb combustion/ion chromatographic detection. 9 Fuel Supply Handbook for Biomass-Fired Power Projects Slagging refers to the fusing of bottom ash, which for adding the ability to reverse the drag chains on the straw occurs at temperatures of about 800­900°C (table dumping hoppers (to make it possible to unplug fuel 2.6). The presence of chlorine and alkali in straw is also jams), and adding three more rolls to each disk screen problematic. These substances react to sodium chloride to reduce the carryover of fine particles that tended to (NaCl) and potassium chloride (KCl) in the flue gas. plug up the hog (Wiltsee 2000). The chlorides are extremely corrosive to the steel of the boiler, particularly at high temperatures5 (DTI 2007a). Teething problems with fuel-feeding systems at the newly established biomass-fired power plants in 2.4.8 Contaminants China are not yet well documented. However, such Besides contaminants within the biomass itself, which problems are reportedly not uncommon. For example, can result in harmful emissions to air and soil if not it is understood that the Henan province plant experi- treated properly, biomass feedstock can be contami- enced such problems because of design inadequacy in nated with materials such as soil or stones, metal, and the Chinese context. plastics. These contaminants can jam fuel-feeding sys- tems. Sand can result in glass formation during com- 2.6 Conclusions and Recommendations bustion (Carbon Trust 2005a). To avoid this type of contamination, it is important to design a proper 2.6.1 Conclusions physical handling mechanism for transferring fuel from The characteristics of the biomass used as fuel have where it is stored to where it is combusted (Carbon a direct impact on the biomass power plant design, Trust 2005a). operation, and performance, including the fuel-feed- ing system, boiler technology, and emissions control. In addition, they have an impact on the best way to 2.5 Example: Some Experiences with handle fuel (collection, transportation, pretreatment, Biomass Fuel-Feeding Systems and storage). Less homogeneous and/or low-quality Experience around the world shows that fuel-feeding fuels need more sophisticated combustion systems. systems in biomass power plants often cope with Some important fuel characteristics are as follows: start-up problems. It is not uncommon that during the first couple of years of plant operation, significant · The moisture content, and closely related to it, the amounts of time and money are spent to solve such calorific value. For thermal conversion, biomass problems as excessive equipment wear, fuel blockages, fuel with a low moisture content is preferred. bottlenecks in the feed system, and tramp metal sepa- · The bulk density has a great impact on supply ration problems. Some examples from North America logistics and transport costs. For low-density fuels are the biomass power plant in Tacoma, Washington (for example, chopped straw), densification prior (United States, operational since 1991), where person- to transportation may be necessary. nel stressed the need to take extra care at the beginning · It is important to have an appropriate match of the project with the design of the fuel-feeding sys- between the biomass particle dimension or parti- tem; and the power plant at Stratton, Maine (United cle size distribution and the fuel-feeding system or States, operational since 1989), where the original combustion technology to avoid frequently occur- owners spent about US$1.8 million during the first ring problems with the fuel-feeding system (for year of operation to improve the operation of the fuel example, excessive wear, fuel hang-ups, and tramp yard. The biomass-fired power plant in Williams Lake metal separation problems). Fuel standards and (British Columbia, Canada; operational since 1993) specifications ensure a proper match between fuel modified the fuel-handling system after start-up by supply and thermal conversion system. · Ash quantity, quality, and composition are impor- tant issues when selecting a biomass fuel. Com- 5. Many of the biomass power plants operating in China have high-temperature boilers and high-pressure grate furnaces in- bustion of agricultural residues results in larger stalled. quantities of ash than combustion of forestry 10 Biomass as a Source of Energy residues. The composition of ash can influence its · Try to make maximum use of secondary residues; melting behavior, which can cause slagging prob- these are usually the cheapest, and they are released lems to occur, in particular for straw. In all cases, centrally and relatively clean. the proper treatment, storage, and sale of ashes · Make sure that plant design and permits allow as should be given due consideration. much fuel flexibility as possible to anticipate poten- tial future changes in the availability of biomass Emissions-reduction measures not only depend on the fuel (fuels sometimes change significantly over type of biomass used, but also on local requirements the years as other opportunities arise or old fuel and the environmental regulations that are in force. sources diminish). · Keep the moisture content of the biomass fuel as Appropriate fuel selection is vital in managing fuel constant as possible for optimal plant operation. supply risk. · Avoid contamination of the biomass fuel because this may lead to operational problems (such as 2.6.2 Recommendations jamming) and excessive emissions. · Carefully determine which biomass type(s) will be · Carefully select emissions-reduction equipment used in the power plant, and which fuel specifica- to meet relevant emissions limitation values, for tions will apply (for example, particle size and dis- example, for nitrogen oxides. tribution, moisture content, and calorific value). · Consider installing a dual-feeding system to allow · Take advantage of available fuel standards and the use of different types of biomass. The installa- specifications to allow a good match between the tion of dedicated boilers for the different types of fuel supply and the energy system. biomass is also an option. 11 3. Biomass Resource Assessment 3.1 Types of Biomass Potential sustainability aspects in biomass resource assessments is within the scope of ongoing research.7 When discussing the availability of biomass, the type of potential is a crucial criterion, because it deter- The implementation of sustainability standards in mines to a large extent the approach and methodology analyses of biomass potential mostly decreases the and thereby also the data requirements of a biomass resulting potential by limiting either the area available resource assessment. There are four distinct types of (for example, by excluding areas designated for nature biomass potential6: conservation) or the anticipated yields (for example, through less intensive management methods in sensi- · Theoretical potential: Describes the ultimate tive areas). This approach is demonstrated in figure resource potential based on calculation or mea- 3.1. Sometimes the application of sustainability cri- surement of the net primary productivity of the teria can increase the biomass potential, for example, biomass. if biomass from landscape conservation activities is · Technical potential: Limits the resource potential included. by accounting for terrain limitations, land use and environmental considerations, collection inefficien- Depending on the intended objective, different types cies, and a number of other technical and social of biomass resource assessments are used. The aim constraints. may be to determine the theoretical potential to assist · Economic potential: Limits the resource potential scenario development. Alternatively, the aim may be by incorporating cost information, such as harvest, to determine the practical "implementation" potential transportation, and processing costs. to assist project developers and investors. In the latter · Implementation potential: Limits the economic case, such issues as alternative land uses, supply logis- potential by taking into account economic, tics, financial viability, and sustainability are explicitly institutional, and social constraints and policy taken into account. In this handbook the second aim incentives. is relevant. In theory, a fifth potential can be considered, the environmentally or ecologically sustainable poten- 3.2 Basic Approaches to Biomass tial, defined as the fraction of the other potentials Resource Assessments that meets certain environmental sustainability crite- Depending on whether the focus is primarily on bio- ria. Around the world there is strong demand for the mass supply, biomass demand, or a combination of inclusion of sustainability aspects in resource assess- both, three basic approaches to biomass resource ments. The concept of sustainable biomass contains assessments can be identified: multiple environmental, economic, and social aspects, and measurement of these aspects--how to measure biodiversity or the impacts of energy crops on climate change--can be complex. The possibility of including 7. The Biomass Energy Europe (BEE) project (http://www.eu- bee.com) is currently developing a standardized methodology for including sustainability aspects in biomass resource assess- 6. The different type of potentials are discussed in more detail ments. Relevant public results of the BEE project will become in annex 4. available in 2010. 12 Biomass Resource Assessment Figure 3.1 The Influence of Sustainability Criteria 3.2.1 Statistical Assessments on Biomass Potential Statistical assessments make use of data from statis- tics on land use, crop yields, crop production, and forest inventories and literature. The statistical data Society are combined with conversion factors, such as yields per hectare and residue-to-crop factors. These factors are based on expert judgment, field studies, or litera- En ture review. In addition, further assumptions are made my vir on no about the fraction of biomass available for energy pro- m Eco en t duction, taking into account biomass or land needed for other purposes. As illustrated in section 3.4, the statistical assessment Technical potential Sustainable potential method is widely used in biomass resource assess- land × yield ments in China. land and yield restrictions 3.2.2 Spatially Explicit Assessments Sources: BTG; Drohm Design & Marketing. The most advanced resource-focused assessments include spatially explicit data on the availability and · Resource-focused methods. accessibility of land and forests in combination with · Demand-driven methods. calculations of the yields of energy crops and forests, · Integrated assessments. based on growth models that use spatially explicit data on, for example, climate, soil type, vegetation Resource-focused methods are normally used to deter- type, and management. When statistics are available mine the theoretical or technical potential, whereas at a detailed level, results from statistical assessments demand-driven methods are used to determine the eco- can be presented in a spatially explicit way. nomic or implementation potential. Integrated assess- ments can be used to determine any of the four types As illustrated in section 3.5, in recent years there have of biomass potential. The general approach determines been various efforts in Europe to use spatially explicit to a large extent the methodology that is used and, in assessments to determine straw availability in selected turn, the methodology determines to a large extent the regions. data that are used. For the purposes of this handbook, resource-focused assessments are the most relevant. 3.3 Steps in a Biomass Resource Assessment Resource-focused assessments investigate the bioen- A resource assessment normally includes the follow- ergy resource base and the competition between dif- ing steps: ferent uses of the resources. That is, the focus is on the supply of biomass energy. Resource-focused assess- · Data collection, which typically covers a large ments typically estimate the theoretical or technical number, type, and scope of data sources (up to sat- potential to produce biomass for energy, thereby usu- ellite imagery, if available). ally taking into account the demand for land to be · Data analysis, which includes sorting out the most used for food production and biomass needed for the relevant data sources and applying residue-to-crop production of food and materials. ratios. · Data completion, which entails filling in the blank Resource-focused assessments can be further divided spots and mapping current biomass utilization into statistical and spatially explicit assessments. processes. 13 Fuel Supply Handbook for Biomass-Fired Power Projects The methods employed to assess biomass resources organic matter affects virtually all soil properties, for will vary, depending on the following: example, physical structure, ease of cultivation, ease of root growth, erosion, nutrients, and biodiversity. In · The purpose for which the data are required. general, more is better. An additional environmental · The level of detail required. benefit is that carbon from the atmosphere is being · The information already available for the particu- locked up. lar country, region, or local site. 3.4 Straw Resource Assessments in China The Biomass Assessment Handbook (Rosillo-Calle and others 2006) presents a step-by-step method for Long-term availability and the ability to contract for determining the availability of agricultural crops and affordable straw are important for the effective opera- residues (annex 5). tion of a straw-fired power plant. To help ensure that sufficient amounts of straw can be acquired year by With regard to assessing biomass resources, two year, a plant owner-developer should be conservative important observations can be made: in assessing the total implementation potential and the share of this potential that can be acquired. Bio- · Determination of conversion factors: In resource mass power companies do not like to be vulnerable assessment, use is often made of residue-to-prod- to local farmers holding out for higher straw prices. uct factors (RPFs) and recoverability factors (RFs). It is therefore common practice to assume a reserve Although much attention has been given to deter- factor of 50­75 percent or more, as well as to reflect mining RPFs, relatively little research seems to have annual resource fluctuations caused by weather, land been done on assessing RFs. use changes, changes in crop mix, price developments, · Need for field surveys: Unless detailed studies from and other factors. the area in question already exist, some detailed field research at chosen sample sites is desirable to In line with the guidelines discussed in annex 6, typi- validate and fine-tune the data. Supporting activi- cal biomass resource assessments in China use sta- ties, such as visiting government authorities, for- tistics on land use, crop yields, crop production, and estry institutes, and large agro-industries, help to forest inventory, and combine them with conversion collect resource data and fill data gaps. factors, such as yields per hectare and RPFs. The latter are based on expert judgment, field studies, or litera- Independent of the application for which the removed ture review. In addition, further assumptions are made biomass is to be used, it is important not to exploit about the fraction of biomass available for energy and remove the maximum potential, for environmen- production. tal and biodiversity reasons (for example, soil fertility). In the Nordic countries (Finland and Sweden), the fol- Applying this method, Li and others (2009) estimate lowing rules of thumb are applied to calculate poten- the annual availability of straw biomass for power gen- tial harvestable forestry residues (AEBIOM 2007): eration at more than 700 million tons (table 3.1). · 75 percent of maximum potential of final fellings, A commonly expressed concern in China is the · 45 percent of thinnings, absence of a "standard" method for biomass resource · 20 percent of stumps from final fellings, and assessment in general and straw resource assessment · 25 percent of the additional fellings (that is, fellings in particular. For example, the observation is explic- of the unutilized increment or roundwood balance). itly or implicitly made by ZERS (2008), NAU (2008), and CECIC (2009b). In an effort to address this issue, For agricultural residues, it is equally important not CECIC (2009b) proposed a Technical Regulation of to exploit and remove the maximum potential. Soil Resource Assessment for Crop Straw Combustion 14 Biomass Resource Assessment Power Generation Project, specifically for the assess- 3.5 Spatially Explicit Straw Resource ment of straw. Assessments: An Example from Europe Despite the expressed concern about lack of a standard, In an effort to assess the technical potential of straw there is a general understanding in China about the from wheat and barley, Edwards and others (2006) proper resource assessment method to be adopted, and combined Europe-wide statistical data on wheat and the CECIC Blue-Sky method mentioned above entails cattle production per administrative region from Euro- a suitable approach. The quality of the survey data and stat with GIS data on land coverage and administra- assumptions is of greater concern. Some efforts have tive boundaries. In addition, supporting information been made to determine agro-ecological, region-specific from straw-for-energy studies was also used. RPFs, but as elsewhere in the world, in China much less attention has been paid to assessing RFs. The study is an interesting example of a spatially explicit resource assessment, and various other To increase the validity of the data and to assess the authors have replicated the approach. It is a useful practical straw potential more accurately, expanding method to determine the potential for large, straw- the scope and coverage of the survey may be consid- fired power plants. In principle, the method is appli- ered in the following ways: cable to any cereal crop, including maize straw and cotton straw, provided that a formula for the pertinent · Carrying out actual field measurements of straw straw-to-grain ratio exists or can be developed. It can usage for all applications. be applied anywhere in the world, including China, · Incorporating time series in the survey (for exam- provided some basic GIS data are available. ple, by repeating the survey in subsequent years). · Incorporating questions related to structural 3.5.1 Straw Potential per Region changes in straw supply and demand, in particular The Edwards and others (2006) assessment started by the future demand of large users of straw, such as estimating the straw yield (straw, tons per hectare of other biomass-fired power plants. arable land) as a function of the grain yield (grain, tons per hectare). Starting from literature values on Table 3.1 Yield of Main Crop Straws in China and Their Heating Values, 2005 Yields of straws/ High heat value/ Low heat value/ Main crops Yield of crops Coefficient 106 tons 106 J/Kg 106 J/Kg Rice 180.59 1 180.59 15.24 13.97 Wheat 97.45 1 97.45 16.67 15.36 Corn 139.37 0.5 278.73 16.90 15.54 Potato 36.48 1 36.48 15.61 14.23 Beans 21.58 0.67 32.37 17.59 16.15 Peanut 14.34 0.5 28.68 18.60 17.23 Rape 13.05 0.33 39.16 15.23 13.81 Fiber 6.82 0.33 20.46 17.37 15.99 Total 509.67 ­ 713.91 ­ ­ Source: Li and others 2009. 15 Fuel Supply Handbook for Biomass-Fired Power Projects Figure 3.2 Straw Yield as a Function of Grain Yield Figure 3.3 Total Straw Production per Region (tons) 1.0 0.9 0.8 straw/grain index 0.7 0.6 0.5 0 0 1 2 3 4 5 6 7 8 9 10 11 grain yield (tons/ha) Source: Edwards and others 2006. the empirical range of harvest indices (grain or above- Source: Edwards and others 2006. ground biomass), Edwards and others (2006) deduced straw-to-grain ratios as a function of grain yield. This Not all produced straw is available for bioenergy. discontinuous relation was smoothed into a conve- The first two constraints that need to be quantified nient function: are environmental limitations and competing uses for straw. Straw = grain × 0.769 ­ 0.129 × arctan [(grain ­ 6.7)/1.5], Environmental constraints prevent collection of straw where grain is the grain yield in tons per hectare and from fields where there are unfavorable soil condi- arctan is the inverse of the tangent function. tions: low organic matter content, risk of degradation processes, limited water resources, and extremes of The function (see figure 3.2) indicates that the straw- climate. In these cases, plowing back the straw into to-grain ratio falls from a maximum of 0.94 to a mini- the soil helps sustain soil fertility. mum of 0.62 as the grain yield increases. Although this formula is based on data for wheat, experts have con- In Europe, the main competing use for straw is cattle firmed that it is also approximately correct for barley, bedding or litter. Significant amounts of straw are also which would be confined to the low-yield, high-straw used in horticulture and mushroom production, and ratio end of the curve. for industrial processes. Exact amounts involved have proved hard to assess. The information published in The function was applied to European statistical various international, national, and regional studies data (Eurostat) for wheat and barley yields, area, is inconsistent, and often based on an expert guess and production, and was linked with GIS NUTS2 lacking documentation of the methodology and termi- regions.8 The resulting estimate of straw potential nology. There are also a few surveys, but comparison from wheat and barley at the regional level is pre- between them is limited for the same reasons. sented in figure 3.3. It is generally accepted that cattle raising is the most 8. The Nomenclature of Territorial Units for Statistics (NUTS, important competitive use of straw. The amount of for the French nomenclature d'unités territoriales statistiques) straw used per head of cattle depends on how long is a geocode standard for referencing the administrative divi- cattle stay indoors (which varies with climate and sions of countries for statistical purposes. 16 Biomass Resource Assessment Figure 3.4 Straw Used per Head of Cattle Figure 3.6 Available Straw per 5x5 km Grid Cell (tons) 3.0 2.5 used straw/head (tonne) 2.0 1.5 1.0 0.5 0 0 1 2 3 4 5 6 7 8 9 total straw per cattle head (tonne) Source: Edwards and others 2006. Figure 3.5 Available Straw per Region (tons) Source: Edwards and others 2006. where SUPH is the straw used per head of cattle in tons per head, exp is an exponential function, and SPPH is the total straw produced per head of cattle in the region in tons per head. Using this equation, the estimated amount of straw used per head of cattle in different regions lies between 0.1 and 2.0 tons per year. Subtracting this estimate of competitive use results in a map of the net surplus of straw at the regional level (figure 3.5). Some regions show a net deficit. 3.5.2 Straw Potential for 5x5 km Grids The Eurostat statistics used in the above calculations Source: Edwards and others 2006. are available at a level of detail corresponding to the NUTS2 regions. Edwards and others (2006) consid- ered this level of detail insufficient, and used CORINE geography), what types of shed are used, and the avail- (Coordination of Information on the Environment)9 ability of straw in the region. Based on the scattered Land Cover data for 2000 (CLC 2000) to spatially dis- data of available studies, Edwards and others (2006) aggregate the information from the statistical regions estimated the straw used per head of cattle (SUPH, onto a regular grid with a cell resolution of 5x5 km. tons per head) from total straw produced per head of cattle in the region (SPPH, tons per head) by an The area of wheat and barley was estimated for each empirical equation (see figure 3.4): 5x5 km grid cell, assuming that the area is distributed SUPH = 2 × [1­ exp (­ SPPH/2)], 9. CORINE Land Cover is a European database of biophysical soil use. 17 Fuel Supply Handbook for Biomass-Fired Power Projects uniformly on the fraction of the cell devoted to the The study by Sims (2007) presents an overview of the CLC 2000 category 211 (arable land). Then straw typical fuel requirements, number of vehicle move- production for each 5x5 grid was found by distrib- ments, land area requirement, and supply radius for uting the net straw surplus for each NUTS2 region various sizes of bioenergy plants (see table 3.2). Table among its constituent grid cells in proportion to the 3.2 illustrates that for bioenergy plants of the size areas of wheat and barley in each cell. This results in a commonly installed in China (20­30 MWe), 2­5 per- more detailed map of net straw availability. cent of the agricultural land area within a radius of 50 km is needed. Li (2008) also proposed a maximum supply radius of 50 km for the collection of maize 3.6 Size of the Biomass Power Plant straw and stalk to feed a 24 MWe biomass CHP plant The optimal size of a biomass power plant depends in Mongolia. on two competing cost factors. As size increases, spe- cific investment costs drop as a result of economies When other large biomass users operate, or plan to of scale, while transport costs increase as a result of operate, in the same collection area, competition for longer biomass transportation distances. The compe- resources can be high. This is what is actually happening tition between these cost factors leads to an optimum in the case of biomass-fired power plants in Shandong size at which the cost of energy produced from bio- and Jiangsu provinces. It is therefore recommended to mass is minimized (Searcy and Flynn 2008). use conservative estimates about the available land area and the associated biomass availability. Apart from the optimal size, many other factors need to be taken into consideration when planning a bio- 3.7 Conclusions and Recommendations mass-fired power plant. To keep transportation costs within limits, it is recommended that a biomass power 3.7.1 Conclusions plant be sited close to where the biomass becomes Many different types of biomass potential exist. For available. And it is always a good idea to locate a investors in Chinese biomass-fired power plants, power plant on a railway or, even better, a waterway. implementation potential is the most relevant. It takes Unless biomass is available at, or near, zero or even into account such topics as alternative land uses, sup- a negative cost, it is also generally recommended to ply logistics, financial viability, and sustainability. generate power in a cogeneration mode to make effi- cient use of the available biomass, and therefore to There are various ways of determining biomass avail- locate the plant near one or more large heat users. It is ability. A resource-focused assessment is the most understood that at many of the biomass power plants relevant approach when investing in a biomass-fired installed in China in 2006­08, these considerations power plant. were not taken into account. Steps in a biomass resource assessment include data When sufficient data are available, the crossover point collection, data analysis, and data completion. The at which further increasing the biomass-fired power better the quality of the data that is available, or can plant size decreases its overall economics can be calcu- be collected, the more sophisticated the assessment lated. Where this is not the case, a rule of thumb can method can be. be applied. A commonly accepted value for the maxi- mum distance that unprocessed biomass can still be Applying detailed residue-to-crop factors may give economically transported is 50 km. Longer transpor- a misleading sense of accuracy, in particular when tation distances may still be acceptable if the biomass information about alternative biomass uses is patchy is first converted into a solid or liquid fuel with higher or poor. energy density, or if water transportation rather than road transportation is used. 18 Biomass Resource Assessment Table 3.2 Typical Scale of Operation for Various Sizes and Types of Bioenergy Plants Heat(th) or power(e) Vehicle movements Land area required to capacity ranges, and Biomass fuel for biomass produce the biomass Type of plant annual hours of operation required (odt/yr) delivery to the plant (% of total within a given radius) Small heat 100­250 kWth 40­60 3­5/yr 1­3% within 1 km radius 2,000 hr Large heat 250 kWth­1 MWth 100­1,200 10­140/yr 5­10% within 2 km radius 3,000 hr Small CHP 500 kWe­2 MWe 1,000­5,000 150­500/yr 1­3% within 5 km radius 4,000 hr Medium CHP 5­10 MWe 30,000­60,000 5­10/day 5­10% within 10 km radius 5,000 hr Large power plant 20­30 MWe 90,000­150,000 25­50/day and night 2­5% within 50 km radius 7,000 hr Source: Sims 2007. Note: odt = Oven dry ton. Transport and land use requirements to meet annual biomass demands when operating at various capacity factors. Biomass yields when produced from forest arisings, agricultural residues, or purpose-grown energy crops are assumed at about 5­10 odt/ha annually. In recent years, several efforts have been initiated 3.7.2 Recommendations around the world to improve biomass resource assess- Use a consistent biomass resource assessment method- ment methodologies. Examples of such initiatives ology that uses not only theoretical RCFs to calculate include the work of the Joint Research Centre of the the available biomass amount, but that also considers European Commission (Ispra, Italy) on the availability the competitive uses of biomass and material losses of straw in the member states of the European Union incurred during biomass collection, storage, and trans- (EU); the EU-sponsored Biomass Energy Europe proj- port caused by climate, humidity, and other reasons. ect that looks at the availability of all types of bio- mass residues and crops across Europe, with a special Carry out field surveys to verify and validate existing emphasis on Central and Eastern Europe; and the biomass resource assessment data. Particular atten- research and field work of Imperial College (Lon- tion should be paid to the following: don, United Kingdom) in, for example, Africa and the Pacific. In China, CECIC Blue-Sky has carried out rel- · The type, amount, seasonality, and usage of local evant work on crop straw assessments. The methods agricultural and forestry biomass resources. developed and results obtained by the initiatives men- · Conversion factors, including RPFs and RFs. tioned can be useful for planning a biomass resource · Time-series data. survey in China. · The current status of local biomass-fired power generation projects (in operation, under construc- For the government of China, it may be worthwhile tion, or awaiting approval) and their fuel demand. to support the development of a spatially explicit assessment methodology for the predominant bio- Try to collect data covering a period of more than a mass resources in China (such as rice straw and corn single year so that seasonal patterns and a trend can stalks). be established. 19 Fuel Supply Handbook for Biomass-Fired Power Projects When conducting interviews, consider expanding cov- collection and harvesting of agricultural or forestry erage by including the following: residues. · Actual field measurements of straw usage for all Do not plan on using more than 25 percent of the applications. biomass that is identified as available. Ideally, a bio- · Use of time series in the survey (for example, by mass-fired power plant should not use more than repeating the survey in subsequent years). 10­15 percent of the freely available biomass. Such · Questions related to structural changes in straw large reserve factors are recommended to ensure that supply and demand. sufficient biomass residues can be acquired year by year for an affordable price. The large reserve fac- When considering a resource survey, make use of tors reflect the annual resource fluctuations caused by handbooks published on this topic, for example, The weather, land use changes, changes in crop mix, price Biomass Assessment Handbook (Rosillo-Calle and developments, and other factors. others 2006). These detailed handbooks present fur- ther useful and practical guidelines for planning and Do not carry out the survey on your own. Rather, carrying out biomass resource surveys. involve an experienced professional consultant who, in an advisory capacity, can give recommendations on the Do not mistake biomass availability for the ability to survey methodology. The adviser can also be charged acquire it under contract. (Aspects of contracting for with the full organization of the survey in the form of biomass are discussed in chapter 6.) interviews, questionnaires, and workshops to get first- hand information from local stakeholders, including key For environmental and biodiversity reasons (for officials from local government agencies, agricultural example, soil fertility) do not exploit and remove the experts, the owners of livestock and planting farms, maximum potential from the sites identified for grain processing factories, and rural households. 20 4. Biomass Supply from Straw 4.1 Introduction The supply chain model developed in Denmark can be replicated in other countries that have highly mecha- During grain harvesting, straw becomes available as a nized agricultural sectors. Section 4.3 introduces straw byproduct. This straw can be used as fuel. In Denmark, supply practice in China. Current straw-supply models the national government adopted a straw-for-energy can at best be qualified as semi-mechanized. Sections policy in 1986. During the last 20 years, extensive 4.4 and 4.5 present short case studies of the straw sup- experience has been gained in Denmark with the use ply arrangements set up at large-scale biomass power of straw for larger-scale CHP generation. Large-scale plants in China and Europe, respectively. straw handling for energy purposes has developed into an independent discipline in agriculture in which par- ticularly large farms and machine pools make invest- 4.2 The Technology and Methods of ments. Most Danish farmers with straw contracts Straw Production produce about 100 tons of straw annually. A few 4.2.1 Production, Raking, and Collection of Straw large farms and machine pools have developed large- Straw is a byproduct of cereal grain production (such scale handling of 10,000­30,000 tons of straw annu- as wheat, rye, barley, triticale, and oats) by combine ally. Straw-for-energy plants were set up elsewhere in harvester. The combine harvester arranges straw in Europe recently (for example, Poland, Spain, and the swaths. United Kingdom), but with a few exceptions, they were smaller scale and primarily meant to generate heat. When rainfall occurs, turning or raking of the swaths is important for the straw quality. This is done by a Section 4.2 discusses the state of the art in high-vol- tractor equipped with a raker (see figure 4.1). ume biomass supply from straw. The section is mainly based on the experience gained in Denmark, which to Once sufficiently dry, the straw can be baled using date is the only country besides China where several a tractor equipped with a baler and an accumulator large-scale, straw-fired CHP plants have been set up. (see figure 4.2). Balers come in several types and sizes: small baler, round baler, medium baler, and big baler. Figure 4.1 Turning and Raking of Swaths Before Baling Figure 4.2 Tractor and Baler in Operation Sources: BTG; Drohm Design & Marketing. Sources: BTG; Drohm Design & Marketing. 21 Fuel Supply Handbook for Biomass-Fired Power Projects Figure 4.3 Loading Straw in the Field load varies from 6 to 18 bales. Over long distances, the tractor is often towing two trailers so that the size of the truckload is as much as 24 big bales. 4.2.3 Long-Term Storage Straw can be stored indoors or outdoors. Indoor stor- age keeps the moisture content stable and prevents mold, minimizing losses. Large storage spaces have a capacity of 1.5­2.5 tons/m2. Outdoor storage is cheap, but it is mainly suitable for short-term storage, and the straw needs to be covered with a tarpaulin. Huisman, Jenkins, and Summers (2002) evaluated Sources: BTG; Drohm Design & Marketing. storage systems for rice straw bales and identified the following storage systems: For Danish power plants, only large bales including · Uncovered so-called big bales and mid bales are accepted. Big · Tarped stacks bales have dimensions of 120 x 130 x 240 cm, a den- · Wrapped bales sity of 140­185 kg/m3, and a weight of 500­800 kg. · Individual wrap A big baler has a capacity of 12­25 tons/hr. In recent · Tube wrap years a midi bale was introduced (dimensions of 120 x · Pole barns 90 x 240 cm). The weight is 425­500 kg per bale. The · Metal buildings advantage of the shorter bale is that the bale density is · Greenhouse loading docks slightly higher and the tractor or truck can carry three · Fabric buildings layers of midi bales instead of two layers of big bales. · Truss-arched tarp The handling capacity of loading is also increased. The disadvantage is that the straw crane in the plant There are substantial differences between stacking has to be modified. capacities, stacking arrangements, system lifetime, and system costs among the different storage systems. 4.2.2 Transporting Straw to Storage Huisman, Jenkins, and Summers (2005) conclude that When transporting straw to storage, various tech- in all cases, except for wrapping, costs decrease with niques and methods are used depending on the local the larger storage quantity. The differences between conditions. Big bales are loaded and unloaded by 800 tons and 4,000 tons are substantial, between front-end loader, trencher, loader tractor, telescope 4,000 tons and 20,000 tons are small, and between loader, or the like. The telescope loader is suitable for 20,000 and 100,000 tons are very limited. Uncovered unloading, because it can reach high up when storing storage of big bales (figure 4.4) is only justifiable for the bales in stacks. The front-end loader is the most short periods (maximum six months) when only the common. Depending on the front-end loader equip- top layer might be lost. For rice straw, pole barns seem ment and lifting capacity, the tractor load capacity and to be the cheapest solution (see figure 4.5). They have stability, and the local conditions, one or two bales are a roof only. Metal buildings are slightly more expen- handled at a time (see figure 4.3). The capacity is high- sive, but are closed on all sides, so better protect the est when handling two bales at a time, but this puts a straw from rain from the side, animals, and arson. severe load on the tractor's front axle, and the stability of the tractor is decreased dramatically if no balancing 4.2.4 Delivery from Long-Term Storage to Power Plant weight is mounted on the back of the tractor. Modified Depending on the distance to be covered, delivery to trucks or truck trailers are widely used. The size of the the power plant takes place by truck or tractor. When 22 Biomass Supply from Straw Figure 4.4 Outdoor Storage of Straw Figure 4.6 Truck for Long-Distance Straw Transport Sources: BTG; Drohm Design & Marketing. Sources: BTG; Drohm Design & Marketing. transporting by haulage contractor, the farmer or the Unloading at the plants by crane often requires the haulage contractor loads the truck, and the haulage bales to be arranged accurately on the transport contractor travels to the plant where plant personnel vehicles. The bales should have a specified dimension unload by forklift truck, overhead traveling crane, and not exceed a certain weight. Unloading by crane or the like. When transporting by tractor, the speed requires the use of big bales, because the power plants of operation and consequently the capacity is con- are equipped for this size of bale (see figure 4.7). siderably lower, with the differences increasing with increasing transport distance. 4.2.5 Handling at the Biomass Power Plant As a result of its low density, the storage of straw is When transporting by truck, the cargo is almost always space consuming. On average, Danish power plants loaded 12 bales on the truck and 12 bales on the truck have storage facilities for eight days of operation at trailer distributed in two layers (see figure 4.6). This is full load. The straw supplier delivers the straw to the also seen in tractor transport, but load sizes of 16 or plant by truck or tractor-towed trailers. The plant 20 bales are also widely used, particularly for trans- takes care of unloading by forklift truck, overhead port over short distances. traveling crane, and the like. Figure 4.5 Pole Barn in California for Storage of Figure 4.7 Unloading 12 Bales in One Operation Rice Straw Sources: BTG; Drohm Design & Marketing. Source: Danish Technological Institute/Lars Nikolaisen. 23 Fuel Supply Handbook for Biomass-Fired Power Projects The bales are weighed on unloading, using either a the NDRC (2008) estimated the amount of annual weighbridge or platform scales. The weighbridge is the available agricultural residues at 681 million tons. fastest because only two weighing operations are car- ried out (gross and tare of the truck). Platform scales Some 80 percent of the agricultural residues are consid- are used when the truck drives onto the platform with ered recoverable for further use. Excluding the amount the front wheels. The truck is weighed every time a bale used as fertilizer, forage for livestock, and industrial is unloaded. A weighbridge is two to three times more materials (such as papermaking), the amount of agri- expensive than platform scales, so the choice between cultural residues available for energy use is more than the two options is a matter of increased investment 300 million tons. However, because about half of crop against increased working time. residues are consumed through direct combustion in rural life, the actual amount of agricultural residues For the determination of the moisture content, a mea- available for centralized biomass-fired power genera- suring instrument equipped with a spear for insertion tion is on the order of about 150 million tons, or 75 into the straw bale is used. The resistance over two million tons of coal equivalent. electrodes is measured and converted into water per- centage. Normally, three measurements are taken of 4.3.2 Straw Collection Practices in China each bale, and the average moisture content is calcu- China has huge volumes of varied, dispersed, and lated. Depending on practice and the wording of the seasonally available types of straw that could be used contract, either a few bales or the whole load may be for power generation. However, relying on traditional rejected. Bales with moisture content of more than collection technology and methods, it is difficult to 20 percent are usually rejected because combustion achieve the high volumes needed to meet the indus- would be too uneven, especially at part load. trial requirements for large-scale, standardized, and continuously available straw. All large power plants are equipped with an automatic crane that lifts the bales from storage to the straw A recent study by CECIC Blue-Sky Investment (CECIC table. The crane is programmed to pick up the bales in 2009a) discusses the methods used at Chinese bio- a certain order, so it is important for the truck or fork- mass-fired power plants for collection, storage, and lift driver to place the bales in marked sections when transportation of straw and stalks. There appears to be wide variety in the current biomass supply chain unloading. Chaff cutters, shredders, or straw dividers and thus little standardization, even in projects with are used to pull apart the baled straw. the same investor, the same fuel type, and the same power generation capacity. The large variety in supply 4.3 Current Status of chain models is hardly surprising--on the one hand, Straw Supply in China the biomass fuel-supply market is relatively new, and on the other hand, each biomass-fired power plant has 4.3.1 Straw Availability in China its unique setting and requires, at least to some extent, In China, straw resources are abundant. There are more its own solution. than 200 kinds of crop straws that can potentially be used to generate energy. The main crops are rice, wheat, Modes for fuel supply include the following: corn, cotton, beans, oil seed, and potatoes. According to the Statistical Yearbook of China, in 2006, the total · Specialized biomass fuel purchasing stations, either area of crops sown was 155 million hectares, and the established by the biomass power plant or operated total output of the main crops was about 510 million by another investor jointly with the local govern- tons. Applying relevant residue-to-crop factors, Li and ment or other organizations. others (2009) estimated the total straw output at more · Cooperation with a professional broker in charge than 700 million tons. This straw comes mainly from of biomass collection, pretreatment, and storage. the eastern region of China. Applying a similar method, A biomass fuel collection agreement will be reached 24 Biomass Supply from Straw between the broker and the power plant. The agree- cannot be met. If the collection radius is expanded, ment will at least cover fuel price formula, fuel collection costs will increase as a result of the higher amount, fuel quality, and method of transaction. transportation distances and costs, and the need for · Cooperation with a multitude (thousands) of var- suitable storage facilities (CECIC 2009a). ied fuel suppliers, including medium- and small- scale biomass fuel brokers and individual rural In response to the lack of suitable feedstock collec- households. tion technology, National Bio Energy Co. Ltd. (the · Combinations of the three modes mentioned above owner of more than a dozen large-scale biomass (CECIC 2009a). energy plants in China) and the Chinese Academy of Agricultural Mechanization Sciences have proposed Modes for fuel collection include the following: a research, development, and demonstration project to develop new equipment for collecting cotton stalks · Rural households: Direct collection and storage of and corn straw. Starting from current technological biomass fuel, and delivery directly to the purchas- research on straw collection, baling, and shredding, ing stations owned by the plant or to the plant site. the research project aims at making a breakthrough in · Fuel brokers: Purchase of biomass fuel in rural areas, key technologies, including mechanical compression, either in the field or from rural households, and automatic baling, cotton stalk collection, and efficient then delivery to the plant purchasing stations, or shredding. The proposal was submitted to the 2009 storage in their own fuel-storage sites. Competitive Grant Facility biomass tender organized · Power plant: Purchase of crop-reaping equipment; by the China Renewable Energy Scale-Up Program, organization of a special team to help rural house- and is being considered for funding. The cotton stalk holds do crop harvesting work nearly free of charge; pickup combine harvester would have a production and then taking charge of biomass collection, stor- capacity of 10­14 mu/hr (equivalent to 0.67­0.93 ha/ age, and transportation (CECIC 2009a). hr), and the corn straw large-square baler would have a production capacity of 9­12 mu/hr (0.6­0.8 ha/hr). Modes for fuel storage include the following: 4.4 Straw Supply in China: Case Studies · Cotton stalks and wood chips with high volumetric weight are usually stacked in the open air. In this section, short case studies are presented illus- · Wheat, corn, and rice stalks are treated by scat- trating straw supply arrangements at selected bio- tering and bundling, then storing them in the fuel mass-fired power plants in China. The information barn; it is less common to process these stalks into was obtained from CECIC (2009a). biomass briquettes (CECIC 2009a). Case Study A: The four case studies in the next section illustrate the 30 MW Biomass Power Plant in Shandong Province biomass procurement modes applied across China. The annual fuel demand at the 30 MW Shandong plant is about 220,000 tons. To ensure biomass supply The current straw collection practice in China can at (cotton stalks and forestry residues, such as bark and best be classified as "semi-mechanized," and it involves wood chips), the plant built eight stations for biomass the application of a traditional chaff cutter for cotton purchasing, storage, and transportation. Site selec- stalk shredding and hydraulic balers for bundling. tion for the purchase stations was mainly based on biomass resource distribution, transportation, natural The experience gained to date shows that mecha- conditions, water resources, and power supply. The nized methods must be used to ensure the quality and biomass supplied to the fuel station is mostly collected quantity of the raw material. Furthermore, the collec- by local fuel brokers. Some fuel brokers have their tion radius needs to be chosen wisely. If the collec- own fuel storage places and pretreatment equipment. tion radius is too small, the demand for biomass fuel The project owner signs contracts with fuel brokers 25 Fuel Supply Handbook for Biomass-Fired Power Projects specifying fuel amount, quality, and price. The bio- complicating fuel supply is the occurrence of the rainy mass fuel is pretreated by biomass purchase stations season in June and July. During this period, wheat or fuel brokers, and there is no further pretreatment stalks cannot dry naturally, and easily decay, resulting at the biomass power plant. in low calorific value and high moisture content, and the effective fuel price will rise accordingly. Case Study B: 12 MW Biomass Power Plant in Henan Province 4.5 Straw Supply in Europe: Case Studies The primary biomass used here includes cotton stalks, wheat stalks, maize stalks, peanut husks, tree bark, In this section, case studies discuss straw supply and wood chips. The biomass fuel is mainly supplied arrangements at biomass-fired power plants in Europe. by small-scale fuel brokers or even directly by local One example each is presented for Denmark, England, rural households. There is no contract between the and Spain--the main European countries using straw plant and the fuel suppliers. To encourage the local to generate power. rural households to transport biomass fuel to the power plant, all involved households received a permit Case Study E: that allows them to enter the tollgate free of charge. 39.7 MW Biomass-Fired Power Plant in Ensted, Denmark The biomass fuel is pretreated at the plant. The biomass-fired boiler plant at the Enstedværket (Denmark) consists of two boilers, a straw-fired boiler Case Study C: producing heat at 470°C, and a wood chip­fired 30 MW Biomass Power Plant in Henan Province boiler superheating the steam from the straw-fired Biomass fuels used here include straw (wheat, maize, boiler to 542°C. The superheated steam is led to the and other), tree bark, and roots. Initially, several straw high-pressure steam system of the Enstedværket Unit purchase stations were built by the biomass power 3. With an estimated annual consumption of 120,000 plant. These were equipped with capital-intensive tons of straw and 30,000 tons of wood chips, the bio- handling equipment, such as bundling machines. The mass-fired boiler produces 88 MW of thermal energy, fuel supply was not satisfactory. Therefore, instead of including 39.7 MW of electrical power. running its own purchase stations, the biomass power plant signed contracts with about 10 large-scale fuel Straw is supplied to the plant by truck, with an average brokers to ensure fuel supply. These fuel brokers have of 40 trucks per day, each containing 24 straw bales their own storage places and bundling machines, and weighing, on average, 500 kg per bale. Five truckloads can pretreat the fuel and then send it to the plant. In supply between 80 m3 and 100 m3 of wood chips to addition, about 100 small-scale fuel brokers and local the plant every day. rural households send biomass fuel to the fuel brokers for pretreatment. Fuel feeding to the straw-fired boiler is fully automatic. The system includes automatic cranes and conveyors, Case Study D: which deliver the straw bales to four feeding lines. The 24 MW Biomass Power Plant in Jiangsu Province straw is burned on a water-cooled vibrating grate. The annual fuel demand (mainly wheat stalk, rice straw, and other yellow straw) at this plant is about Case Study F: 300,000 tons. Fuel brokers and local rural households 38 MW Straw-Fired Power Plant in Ely, United Kingdom have their own storage places and bundling machines, The 38 MWe straw-fired power plant in Ely (United and they can pretreat the fuel to ensure the fuel supply. Kingdom) was the world's largest at the time of its con- Because of competition from seven biomass power struction. It consumes 200,000 tons of straw per year plants within a 150 km radius, the regional avail- and is also capable of burning a range of other biofuels ability of fuel is limited and biomass fuel needs to be and up to 10 percent natural gas. The main fuel of collected from up to 150 km distant. A second factor the plant is agricultural straw from the production of 26 Biomass Supply from Straw cereals, such as wheat, oat, barley, and rye. The straw is Currently, a wide variety of biomass collection, stor- supplied to the plant in so-called Hesston bales weigh- age, and transportation modes are evident in China, ing approximately 500 kg each. The straw bales are even in projects with the same investor, the same fuel stored at the plant in two separate barns, each contain- type, and the same power generation capacity. There ing straw for approximately 24 hours of operation at seems to be little or no standardization. This is hardly full plant load. The handling of straw bales in the barns surprising since, on the one hand, the supply market is is performed by large dual-rail cranes. An automated relatively new and immature and, on the other hand, conveying system transports the straw bales from stor- each biomass power plant has its unique setting and age to the firing system of the steam boiler. requires to some extent a different solution. Case Study G: Transport logistics are crucial for economic power 25 MW Straw-Fired Power Plant in Sangüesa; plant operation. For low-density straw, the collection Navarra, Spain area should be kept as small as possible. When the col- The Sangüesa plant consumes approximately 160,000 lection radius expands, collection costs increase as a tons of straw and corn stover per year. The straw is result of the higher transport distances and costs, and supplied by farmers growing crops within a radius of the need for suitable storage facilities. Densification of 75 km from the plant site. The bales of straw arrive at straw in the form of pellets or briquettes may be con- the plant on trucks. The trucks deliver the fuel to the sidered, depending on the transport distance. straw barn storage area where the moisture content and weight of the bales are measured and the straw is Because of its seasonal availability, a large portion stored. The data recovered from the moisture content of the straw used at the power plant will need to be and weight measurements are registered and form the stored for several months. Given that there is only a basis for the purchaser in determining the price for the two-month harvest window for straw, large volumes straw. The barn is divided into three sections, and it of storage are needed. The optimal storage size is dif- has a storage capacity of three days of operation. ficult to determine because of the various issues that need to be considered (such as fire risk and protection The power plant is equipped with three automatic dual- against rain). The storage at capacity at the power rail cranes. These cranes unload the trucks and store plant site is usually very limited (in the range of a few the straw in piles according to a prearranged system. days) because of the daily volumes needed (500­1,000 The cranes also feed the straw bales onto automatic tons per day). On average, Danish power plants have conveyors that transport the straw from the straw storage facilities for eight days' operation at full load. barn to the boiler building. When the bales arrive at the feeding system, an automatic knife cuts the twines. A biomass resource assessment that also considers The straw then enters a disintegrator where the straw current and future competing uses for raw materials is bale is loosened before being fed into the boiler at the required to assess the long-term availability of straw. required, controlled flow rate. For example, the biomass power plant in Jiangsu province (section 4.4, case study D) had to cope with the limited regional availability of fuel because of 4.6 Conclusions and Recommendations competition with seven other biomass power plants 4.6.1 Conclusions within a 150 km radius. To tackle this supply bottle- When using straw for energy applications, the logisti- neck, it is worth exploring the use of a broad biomass cal principles are basically the same as for traditional fuel mix so as to limit vulnerability to market change, straw applications. However, the scale of operation short-term weather conditions, and long-term climate is significantly larger, in particular related to storage change. Long-term biomass contracting (see chapter and to ensuring the proper moisture content and year- 6) is a further instrument to help secure the power round availability. plant's fuel supply. 27 Fuel Supply Handbook for Biomass-Fired Power Projects The challenge for Chinese straw suppliers is to orga- To ensure economies of scale, Chinese power plant nize the highest throughput in straw collection at the operators and fuel suppliers may unite their efforts to lowest cost. Important lessons can be learned from develop high-throughput straw-collecting equipment. Denmark, where practical experience operating bio- The government of China should consider catalyzing mass power and CHP plants on wheat straw has been such cooperation. gained since the late 1980s. 4.6.2 Recommendations The Danish experience will not be replicated directly · Make sure that the transport logistics of straw are in China, because local conditions and practices in well managed because they make up a high share China must be taken into consideration. For example, of the delivered fuel costs, and they impose a limit China has more farmers, a lower degree of mechaniza- on the maximum plant size. tion, different types of cereal crops, and different unit · For high-capacity power plants, use large rectangu- prices and price structures. lar bales and a weighbridge. · Obtain straw from at least a few different fuel sup- Although Chinese rural labor is cheap, the experience pliers (brokers) to prevent a single fuel supplier from Denmark suggests that highly mechanized meth- (broker) from controlling the fuel price (see section ods are required to ensure the quality and quantity of 4.4, case study B). the straw supply. In China, as elsewhere, the straw- · Do not store straw outdoors for long (maximum harvesting season lasts only two months. Therefore, six months). Indoor storage is more expensive, but a certain degree of mechanization and automation of it keeps the moisture content stable and prevents the straw harvesting process may be warranted. This mold, thus minimizing losses). is recognized by China's largest biomass-fired plant · Depending on practice and the biomass contract, operator, National Bio Energy (NBE). Together with do not accept straw with a high moisture content the Chinese Academy of Agricultural Mechanization (usually straw with more than 20 percent moisture Sciences, NBE has initiated the development of new content is rejected in Denmark). Fuel combustion equipment for collecting, baling, and shredding cotton would become too uneven, especially at part load stalks and corn straw. operation. 28 5. Biomass Supply from Forestry Residues 5.1 Introduction Extraction of forest fuel in conjunction with final fell- ing not only supplies a source of renewable energy 5.1.1 Forestry Residues Types and Yields but also provides higher revenues for forest owners, Forestry residues consist of small trees, branches, because regeneration is promoted through the removal tops, and unmerchantable wood left in the forest of harvest residues from the final felled area. Branches after the clearing, thinning, or final felling of forest and tops equal 20­30 percent of the biomass above stands. Worldwide, experience with the large-scale use the stumps. In the Finnish Wood Energy Technology of forestry residues for power production is limited. Programme, the Technical Research Centre of Finland Actually, in most countries, forestry residues are not (VTT) investigated yields of biomass residues under collected at all for this purpose. The main barriers to a typical management regime of a southern Finnish their use are high transportation, harvesting, and han- forest stand (Hakkila 2004). The results are presented dling costs. in table 5.1. The heavily forested Nordic countries of Finland and 5.1.2 Forestry Residues Production Cost Factors Sweden may be the only countries where forestry While fossil fuels occur in large deposits and can be residues are used for power production on a relevant produced at a constant cost, forest fuels are scattered scale. The two countries have promoted this applica- and must be collected from a large number of loca- tion for some time by, among other things, support- tions. The production costs of these residues depend ing the development and optimization of harvesting, on many steps within the logistics chain--such as handling, and transportation technology and logistics. harvesting (extraction), comminuting (chipping or Advanced technologies in the fuel supply and logistics crushing), and storage and transport--as well as the chain have enhanced the use of forestry residues as scale of operation, the biomass source, and the quality a new raw material resource that is efficiently used requirements placed upon the biomass (figure 5.1). in the form of wood chips. These technologies are still under development, and improvements are made The largest fraction of the procurement costs consists continually. of terrain and road transport. Therefore, the core of forest chip logistics is the control of transportation. Three main sources of forestry residues can be iden- Converting the biomass into transportable form with tified: slash from final fellings, slash and small trees a chipper, crusher, or baler also is an essential part of from thinnings and clearings of young stands, and the logistics system. unmerchantable wood. The forestry residues or "for- est slash" generated at final fellings include the waste A significant gap exists between the cost of fuel from left on the ground after the forestry operations have the early thinnings and that from final cuttings. The taken place (wood harvesting) and the excess pro- gap is caused by the high cost of cutting and bunch- duction that has not been used. Forest slash mainly ing small trees from thinnings; in the other phases of consists of the tops of trunks, stems, branches, leaves, the procurement chain, cost differences are modest. stumps, and roots. In Sweden, slash from final fellings If no stumpage is paid, the cost level under Finnish constitutes the largest share (over 71 percent in 1996 conditions stood at 12.8/MWh for whole-tree chips and even more in 2003). and 8.4/MWh for logging residue chips (2002 data). 29 Fuel Supply Handbook for Biomass-Fired Power Projects Table 5.1 Forest Productivity in Finland Yield of timber Biomass residues Treatment Stand age (years) (m3/ha) m3/ha toe/ha GJ/ha Precommercial thinning 10­20 -- 15­50 3­9 125­375 1st commercial thinning 25­40 30­80 30­50 6­9 250­375 2nd commercial thinning 40­60 50­90 20­40 4­8 165­335 3rd commercial thinning 50­70 60­100 20­40 4­8 165­335 Final harvest 70­100 220­330 70­130 13­24 545­1005 Total during rotation n.a. 360­600 155­310 30­58 1,255­2,430 Source: Hakkila 2004. Note: n.a. = Not applicable. Annex 7 presents some of the main findings from the mainly by trucks with demountable body systems and Finnish research into reducing biomass supply costs. containers (Emilsson 2006). A number of different forest fuel extraction systems are 5.2 Harvesting (Extraction) applied after mechanical final felling. These systems 5.2.1 Extraction in Connection with Final Felling have somewhat divergent sequences and techniques: Felling adapted for forest fuel extraction is performed with conventional machinery, but according to a spe- · The forest fuel can be transported directly to an cial method. When felling, the harvester operator energy plant or terminal from the temporary depot works so that forest fuel, that is, branches and tops, in the forest and be chipped or crushed at the plant is gathered into stacks. The trees are felled and tilted or terminal. One problem with this system is that over forward, and the fuel is stacked 100­150 cm high it is difficult to make the load sufficiently compact and laid alongside the driving passage. After felling, the stacks are often left in the clearing to shed their crown foliage. Crown foliage contains high concen- trations of nutrients that should be left to benefit for- Figure 5.1 Typical Cost Structure of Forest Chips in est soil. The crown foliage should preferably be spread Finland--Prices at Plant, Excluding VAT, 2002 evenly over the final felled area, but this is difficult to 16 carry out in practice. The stacks are hauled out with a 14 overhead forwarder to a roadside landing, often in the summer 12 truck transport after felling. The tractor should be equipped with an chipping at landing open gripper to avoid bringing up rocks and soil with 10 cost, /MWh off-road transport the load. To take large loads, it should also have some 8 cutting kind of extended trailer, and loading should be done 6 laterally and back to front. The machinery does not 4 have to be otherwise modified for forest fuel extrac- 2 tion. The fuel should be deposited in stacks at an open, dry place where it can continue to dry. Stacks can also 0 logging whole-tree be covered with paper and anchored by a few bun- residue chips chips dles of harvest residues. Chipping is carried out at the stacks, and forest fuel chips are transported onward Sources: BTG; Drohm Design & Marketing based on Hakkila 2004. 30 Biomass Supply from Forestry Residues for transport to be financially viable. Technical for processing. Here, as with extraction in conjunc- refinements aimed at solving this problem are being tion with final felling, there are a number of variants developed. or combinations for the extraction (Emilsson 2006): · Chipping can be carried out in the felled area with a mobile chipper, which then dumps the forest fuel · Conventional thinning harvesters are used for thick- chips in containers parked at a forest roadside or in er stands. The method is similar to that used for a shuttle transporter. mechanical final felling. · The forest fuel is sometimes hauled out of the felled · Chipping can be carried out in the stand, preferably area to a forest road immediately after felling, with along skid roads, after which the chips are dumped crown foliage still attached. This method may be in containers. preferable on severely acidified soil with a high · One interesting variant is "long tops," a method nitrogen deposition, since crown foliage extraction of thinning in which the harvester cuts the tops at reduces the nitrogen load. Here as well, chipping a diameter thicker than normal, and the forest fuel can be done at the roadside or after transport to a is extracted as long, untrimmed tops. This yields heating plant or terminal. When green forest fuel more forest fuel at the expense of pulpwood. that has not shed its crown foliage is extracted, · Forest fuel can also be extracted in connection with the need for ash recycling to compensate for the restoration of meadowlands and pastures, visibility extraction increases. clearing, and so forth, using technical systems simi- · There are also techniques for bundling fresh forest lar to those used for extraction in conjunction with fuel with the crown foliage still attached into log-like thinning and clearing. bundles that can essentially be handled like round timber. The main advantage of this technique is that 5.3 Comminution standard timber trucks can be used, and further transport of timber and forest fuel can be coordi- Comminution (sizing of the fuel) is the most impor- nated. The method requires appropriately dimen- tant phase in the forest fuel production chain, since it sioned crushers at the heating plant or terminal. has a crucial impact on system efficiency. Comminu- tion may take place at (a) the roadside or landing site, 5.2.2 Extraction in Connection with Clearing (b) the source, (c) the end-use facility, or (d) a fuel and Thinning terminal. Integrating forest fuel extraction with a forestry oper- ation, such as thinning or clearing, is a relatively new A forest fuel production system is built around the practice. Clearing entails a net expenditure for the comminution phase. The position of the chipper or forest owner and, as a result, is sometimes neglected, crusher in the biomass procurement chain largely leading to large areas of young forest with high stem determines the state of biomass during transportation numbers that must be dealt with. These stands are and, consequently, whether subsequent machines are ideal for extraction of forest fuel. For cost reasons, dependent on each other. When there is such depen- extraction is carried out mainly in conjunction with dence, the production system is "hot," and the chain mechanical thinning or clearing. Since the extraction is referred to as a hot chain. When there is no such volume is less than in connection with final felling, dependence, the production system is "cool," and the the financial pressure is also greater. An accumulating chain is referred to as a cool chain. multitree-handling harvester is often used, which cuts stems, accumulates them, and puts them in bundles 5.3.1 Comminution at Landing alongside the skid road for hauling to a landing. This Comminution at a landing or roadside is the tradi- technique enhances performance considerably com- tional option for forest chip production. The biomass pared with single-tree handling by making hauling is hauled by forwarders to the landing and bunched easier. The forest fuel can either be chipped at the stack into 4­5 m high piles. The forwarder operates inde- or transported directly to a terminal or boiler plant pendently of the chipper. Comminution is performed 31 Fuel Supply Handbook for Biomass-Fired Power Projects Figure 5.2 Forest Chips Production Chain Based on Chipping at Roadside (Landing) Source: VTT, Alakangas. at the landing using farm tractor­driven chippers in Landing chippers do not operate off-road and can there- smaller operations and heavy truck-mounted chippers fore be heavier, stronger, and more efficient than terrain or crushers in large-scale operations (see figure 5.2). chippers. They are reliable, their technical availability is high, and they have a long life span. They need to be Chips are blown directly into a 100­130 m3 trailer highly efficient. To avoid peak stresses for the machin- truck. The chip truck is typically equipped with either ery because of sudden variations in the feeding rate, the a bottom conveyor or a side tipper, and it weighs about chipper should have a long feeding table, facilitating 23 tons unloaded. This allows a maximum load of 37 a smooth raw material flow. Drum chippers are more tons of chips to be transported (when the allowable suitable than disc chippers. Drum chippers produce total mass is 60 tons, as in Finland). With very moist more homogeneous, that is, even-quality chips (with chips, overloads are possible, whereas with dry chip fewer splinters) and are also not as sensitive to impuri- loads, total weight stays well under the upper limit. ties. If the biomass, such as stump and root wood, is contaminated by stones and soil, it is possible to use When comminution takes place at the landing or crushers that are more tolerant than chippers. roadside, the chipper and chip truck are dependent on each other. For that reason the system is hot and The productivity of roadside chipping is affected by the vulnerable to machines waiting on each other, which characteristics of the raw material, storage, and work- can result in reduced operational efficiency. Thus, the ing site arrangements, as well as the properties of the logistics between the chipper and the chip trucks is chipper. In general, productivity varies between 40 bulk crucial to keeping the fuel supply economically viable. m3 and 80 bulk m3 per effective working hour. It is nor- However, if the chipper and chip truck belong to dif- mally faster to process fresh forestry residues than dry ferent contractors, optimization of the logistics may raw material. An overly careful utilization of the bottom be difficult. bundles of forestry residues is not profitable. Significant extra costs may be incurred because the impurities from Another problem is that a wider landing area is required the ground might damage the chipper knives. than in the alternative systems. This is because of the large roadside inventories of biomass and the simulta- To prevent the system from overheating, the truck- neous presence of the chipper and the truck. mounted chipper and chip truck can be replaced by a 32 Biomass Supply from Forestry Residues Figure 5.3 Chipper Truck Source: L&T Biowatti. single chipper truck (see figure 5.3). This truck blows load is hauled to the roadside and tipped into a truck the chips directly into a container and then hauls the container, which may be on the ground or on a truck load to the plant. Since the chipper truck is equipped trailer (see figure 5.4). with a chipping device and crane, load capacity suf- fers, and the radius of operations around the plant is Because a single machine carries out both the com- reduced. Conversely, because only one single unit is minution of biomass and the off-road transport of needed, the chipper truck is suitable for small work chips, the cost of shifting machines from site to site sites and for delivering chips to smaller-scale plants. is reduced, and smaller forestry sites become com- mercially viable. Moving the terrain chipper from one 5.3.2 Comminution at the Source working site to another can be accomplished either Comminution in the terrain, or at the source, requires on a low-bed trailer or, for short distances, by driving a highly mobile chipper suitable for cross-country the terrain chipper on roads. The use of containers operations that is equipped with a tippable 15­20 m3 reduces the interdependence between the chipper and chip container. Terrain chippers are typically built on the truck, although it is not entirely removed, and the a forwarder chassis. The chipper moves in the terrain system remains somewhat hot. Large landing areas on strip roads and transfers the biomass with its grap- are not required, but a level and firm site is necessary ple loader to the feeder of the chipping device. The for the truck containers. 33 Fuel Supply Handbook for Biomass-Fired Power Projects Figure 5.4 Forest Chips Production Chain Based on Terrain Chipping Source: VTT, Alakangas. For off-road operation, the chipper must be as light as other, and hot chain problems are avoided. The tech- possible, while still sufficiently strong and stable. Even nical and operational availability of the equipment so, terrain chippers tend to be too heavy for use on increases, which raises productivity and reduces costs. soft soils, while the use of crushing equipment in ter- Furthermore, control of the procurement process is rain is out of the question. A terrain chipper requires facilitated, demand for labor is decreased, and the flat and level ground and, because of its small load control of fuel quality is improved. Mobile chippers size and slow speed, its range is less than 300­400 can be replaced by heavy stationary crushers that are m. Snow causes problems in the winter and results in suitable for comminuting all kinds of biomass, includ- a higher moisture content unless the terrain chipper ing stump and root wood and recycled wood. operates at a landing. Under Finnish conditions, comminution at the end- By using exchangeable chip containers for long-dis- use facility is the most economic processing option, tance transport of the wood chips, there is no danger provided the processed volumes are large (only large of forming a hot chain, provided there are sufficient plants can afford a stationary crusher) and the trans- containers to be filled. Chip trucks use typically 30­50 portation distance does not exceed 55 km. The larger bulk m3 chip containers, two or three of which can be the fuel flow, the more obvious the advantages become. transported at the same time, raising the total volume Requirements include a heavy crane and a fairly large of the load to 80­100 m3. storage and processing space. Noise and dust emis- sions can be a problem, and they need attention. The cost competitiveness of a terrain chipper is fairly weak for long forest haulage distances. When large The main challenges of this processing option are volumes of forest fuels are produced, the terrain chip- related to long-distance transport of forestry residues. ping system becomes difficult to control. Truck transportation of biomass traditionally takes place in the form of loose forestry residues, whole 5.3.3 Comminution at the End-Use Facility trees, or pieces of stump and root wood. The low bulk A third option for processing forestry residues is chip- density of the biomass is the weak link in the system. ping or crushing at the end-use facility. In this system, Without compacting the forestry residues, truckloads chipping and trucking are fully independent of each remain very small. 34 Biomass Supply from Forestry Residues Figure 5.5 Forest Chips Production Chain Based on Comminution of Loose Residues at an End-Use Facility Source: VTT, Alakangas. The traditional approach to increasing the truckload is transportation. Building on a Fiberpac design, intro- to compact the load or extend the load space, or both. duced earlier in Sweden, Timberjack (now part of and A new approach is the baling of loose forestry residues renamed John Deere) further developed the technol- into composite residue logs (CRLs). The baling takes ogy that resulted in the 1490D residue baler (see fig- place in the forest at the woodlot before transport. ure 5.6). The two approaches are discussed below. In this system, forestry residues are compressed and Comminution of Loose Forestry Residues tied into 0.7 m diameter, 3 m long bales or CRLs. A The principles of processing loose forestry residues at bale of green residues weighs 500­550 kg and has an end-use facility are presented in figure 5.5. Long-dis- an energy content of about 1 MWh. Bales are trans- tance transportation of forestry residues imposes sev- ported to the roadside using a conventional forwarder eral requirements on the transportation equipment: (figure 5.7) and are stored at the roadside for one to three months to dry (figure 5.8). The bales are trans- · The load space of the truck should be built accord- ported to the power plant using a conventional tim- ing to the maximum allowable dimensions. ber truck. About 12 bales form one forwarder load, · The load space must have a closed bottom and and 65 bales or 30 tons form one truckload (truck- sides. · The trucks should be equipped with special cranes Figure 5.6 Timberjack 1490D Residue Baler suitable for loading and unloading residue, as well as for compacting the load. · Special forestry residue grapples are more suitable for loading than are normal timber grapples. The transportation density of forestry residues can be improved by using separate hydraulic compressing cylinders and bolster bars. The disadvantages of this system include extra costs and a fairly complicated equipment structure. Comminution of Baled Forestry Residues Baling forestry residues is one way of compacting raw Source: Drohm Design & Marketing/Deere & Company material to improve the productivity of long-distance image gallery. 35 Fuel Supply Handbook for Biomass-Fired Power Projects Figure 5.7 Loading CRL Bundles on a Forwarder Figure 5.8 Storage of CRL Bundles Sources: BTG; Drohm Design & Marketing/Deere & Company image gallery. Source: Drohm Design & Marketing/Deere & Company image gallery. In the most efficient cases, the CRLs are unloaded directly from the truck to the feeding table of the crusher. The baled residues processing chain is illus- trailer combination). CRLs can also be transported to trated in figure 5.9. the end-use site together with commercial timber, for example, pulpwood. At some plants in Finland, long- The advantages of CRLs in large-scale operations distance transportation is done by rail. become clear when considering not only the costs from separate work phases of the processing chain, but also Unloading the CRLs takes place at the end-use site with logistics, operational availability, process control, reli- equipment similar to that for unloading pulpwood. ability, scaling, and environmental impacts: Figure 5.9 Production Chain Based on Composite Residue Logs Source: VTT, Alakangas. 36 Biomass Supply from Forestry Residues · Machines operate independently of each other. differ greatly from comminution at plant. The termi- · Flexible integration in the procurement of indus- nal may be paved, and the use of a crusher will be trial wood. possible. · Accurate real-time information about the inven- tories. A terminal is a tool for controlling the procurement · Fewer problems with noise, dust, and litter. process. Biomass can be stored at the terminal uncom- · Reduced space requirement; simple storage. minuted and processed during the winter season when · Reduced transport and overhead costs. the demand for fuel is high and working conditions at · Improved control of fuel flow and reliable delivery. the forest end are difficult. The arrangement makes it possible to apply baling technology to supply forest The advantages must be weighed against the extra chips to smaller energy plants that do not have sta- cost of baling. In Finland, the system based on CRLs tionary crushers. and comminution at a plant quickly became popular. The organizations responsible for the procurement of 5.4 Biomass Fuel Storage raw material for the forest industries found the baling technology an attractive way to integrate fuel produc- According to Vares and others (2005), the amount of tion into their operations. A range of other countries fuel stored at the boiler plant and thus the capacity (Austria, the Czech Republic, France, Germany, Hun- of the fuel storage facility depends on several factors, gary, Italy, Portugal, Spain, Sweden, Switzerland, and including the type of agreement with the fuel supplier the United States) have tested the John Deere (previ- (see chapter 6). A minimum reserve is necessary to pro- ously Timberjack) residue baler, with some of them vide continuous fuel supply, and a maximum reserve is using it for commercial operations. required for providing fire safety. Furthermore, there is always a danger of breathing in the allergy dust or It may still be economical to transport forestry resi- micro-organisms in woodchip storage. For that rea- dues over short distances to the plant as unprocessed son, it is important not to work alone in the storage loose material. facility, and important for the storage side to be well ventilated. Covering forestry residues prevents mold 5.3.4 Comminution at a Terminal growth during extended storage. Comminution at a terminal is a compromise between comminution at a landing and at the end-use facility. The best way to store forestry residues is to lay them Biomass is hauled uncomminuted to the terminal for on a waterproof surface (cement or asphalt) protected size reduction, and then transported to the plant as by a cover located in a sunny and ventilated site (Fran- chips. cescato and others 2008). However, depending on the management of the biomass supply chain and the If the network of terminals is dense, the distance from availability of storage space beside the biomass-fired the forestry site to the terminal remains short. The sys- power plant, forestry residues are stored either at the tem does not differ much from the traditional option roadside or at the power plant location. Short-term where comminution is carried out at a landing. storage for one to several days of uninterrupted opera- tion is always required at the biomass power plant. If a fuel producer operates only a few terminals--and they are located far from the biomass sources--off- 5.4.1 Storing Forestry Residues at Roadside road transport with a forwarder and on-road trans- According to Savolainen and Berggren (2000), stor- port with a truck will be separate operations. The size age of forestry residues at a roadside landing needs to of the terminal will be larger, and the system will not comply with the following: 37 Fuel Supply Handbook for Biomass-Fired Power Projects · Planning must be done carefully because of the The fuel storage at the biomass-fired power plant "hot chain," for example, where the unavailability always consists of at least two parts: of one unit affects the whole chain. · The landing must be spacious, level, and well bear- · Interim storage with capacity for a few days of ing. No stumps, big rocks, or any other obstacles plant operation (typically between two and eight that could hinder movements should be at the site. days). · The landing should not be close to electrical or tele- · A terminal with an automated boiler fuel sup- phone lines. ply, with capacity of up to 24 hours of plant · The landing should be spacious enough for vehicles operation. to turn and pass. · The landing should have the necessary space for These two types of storage are usually situated in the the piles of forestry residues--approximately 10 m same building, although they may be located sepa- in width for every 100 m3 of forestry residue if the rately. At smaller power plants, a bulldozer fills the pile is approximately 5 m tall and wide. terminal and hauls forestry residues from the interim storage. At bigger power plants, an automatically Some other important aspects concerning roadside operated crane is used for filling the terminal. storage are the following: 5.5 Bioenergy Fuel Chain Case Studies · Forestry residue storage piles should be as large as from China possible. In practice, the rear edge of the pile may be located at a maximum distance of 5­6 m from Although it is understood that at least some of the the edge of the road. Chinese biomass-fired power plants use forestry resi- · Small piles get wet easily during storage. dues as one of their feedstocks (for example, the 30 · A few bundles of whole trees (or tops) should be MW power plants in Shandong and Henan provinces, placed transversely on the bottom of the pile to which mainly use bark and wood chips), few docu- protect forestry residues from contamination and ments on assessing forestry residues for this purpose frost during the winter. seem to be publicly available in English. · Forestry residues should be placed in a roadside pile with the butts of the trees facing the road. 5.6 Bioenergy Fuel Chain Case Studies from Europe · Piling crosswise should be avoided. 5.4.2 Storing Forestry Residues at Biomass-Fired As discussed in section 5.1, Finland and Sweden have Power Plant the most experience using forestry residues for power According to Vares and others (2005), biomass stor- production. In the frame of the EUBIONET-2 project age at the power plant must meet the following basic (www.eubionet.net), funded by the European Com- requirements: mission, more than 30 supply chain case studies were developed, describing biomass supply chains in use at · Adequate protection of the fuel from the impacts of bioenergy plants across Europe, including in Finland weather, and from surface and ground water. and Sweden.10 · Mechanized storage and, for larger capacities, automation. · Access for delivery vehicles to unload directly in 10. Case studies #2 Forest residue supply chain for CHP plants the storage or mechanized reception unit. in Central Finland, and #7 Supply chain for wood chips from early thinning in Sweden. The case studies are available at eu- bionet2.ohoi.net. 38 Biomass Supply from Forestry Residues Figure 5.10 A Wood Chips Delivery System Integrating Different Supply Concepts Vapo Company--Organizing wood chip delivery Collecting felling residue (harvester-forwarder) Purchasing ground wood to storages along roads Transportation in Transportation in forests--tractor trailer forests--forest tractor Terminal chipping--TT97 Terminal chipping--TT97 Transportation lorry tractor chipper RMT lorry chipper Transporting chips semi rigid lorry Transporting chips--3 containers Chipping--TT97 Chipping--TT97 RMT Terminal storage tractor chipper lorry chipper Transporting chips--articulated lorry Toppila heat plant, 267­315 MW, fuel usage 3,800 GWh, forest chips 42 percent (equals 30,000 m3) Sources: BTG; Drohm Design & Marketing based on Pöysti 2005. Another valuable source of case studies is the 5EURES 5.7 Conclusions project, which was also funded by the European Commission.11 The challenge for Chinese forestry residue suppliers is to organize the highest throughput in fuel collection Figures 5.10 and 5.11 present graphical representa- at the lowest cost. Important lessons can be learned tions of two sample forestry fuel supply systems, from Finland and Sweden, where practical experience applied by the companies VAPO and UPM-Kymmene, operating biomass district heating, CHP, and power respectively (Pöysti 2005). Earlier sections of this plants on forest fuel has expanded considerably over chapter, in particular sections 5.2­5.4, discuss the var- the last few decades. ious unit operations that make up the respective fuel supply chains. Note that each biomass fuel situation The Nordic experience with the large-scale supply of will require a customized supply system. forest chips will not be replicated directly in China because the production methods and cost breakdown of forest chips vary considerably between countries and regions. Due consideration will be given to local 11. Study material from the project 5EURES--Bioenergy Pro- conditions and practices in China. Generally, the cost duction Know-How to Five European Regions is available at depends on how well the unit operations in the sup- www.ncp.fi/koulutusohjelmat/metsa/5Eures/study_material_ ply chain are organized and structured. Furthermore, index2005.htm. 39 Fuel Supply Handbook for Biomass-Fired Power Projects Figure 5.11 A Forestry Residues Supply System A forest fuel supply chain will be built around the chip- Based on Bundled Slash Delivery per or crusher, since comminution or sizing of the fuel is the most important phase in the production chain. UPM-Kymmene Corporation--Organizing bundled slash delivery To select the most-suitable comminution system, the following issues are important to consider: Piling felling residue with harvester-forwarder · Hot chain versus cold chain: In roadside chipping the chipper and truck are dependent on each other Bundling slash (Timberjack/Fiberjack 370 slashbundler) (hot chain). As a consequence, the potential operat- ing time of the chipper or chip truck may be wasted by waiting, resulting in a low degree of capacity Transporting slash bundles in forest (Forest tractors) utilization and high chipping costs. Chipping at an end-use facility makes the chipper and truck inde- pendent of each other (cold chain) and makes it Transporting slash bundles long distance (timber lorries) easier to ensure a high degree of capacity utiliza- tion and thus to achieve low chipping costs. · Load volume: The low bulk density or load volume Alholmens Kraft heat plant, 580 MW, fuel usage 3,500 GW forest chips 12 percent (equals 200,000 m3) of unprocessed material is the weak link in the end- use facility chipping system. New technology (for Sources: BTG; Drohm Design & Marketing based on Pöysti 2005. example, the bundling of slash or the delimbing of small trees) helps to improve the bulk density and reduces transport costs. the efficiency of a procurement system is highly depen- · Investment costs: The costs of centralized commi- dent on the environment and infrastructure in which it nution equipment are high, and an end-use facility operates. Economic, social, ecological, industrial, and chipping system is suitable only for large plants. educational factors, as well as local traditions, also The roadside landing chipping system is suitable have an effect. for smaller energy plants. Selection of the forest fuel harvesting technology The cost and productivity of the forest chip supply requires a complex technical analysis that takes into vary greatly between countries because of differences account in forest resources, annual harvest, and cost structure of machinery. Often the costs depend on how well all · Annual need for forest fuels and other fuels. the operations featured in the supply chain are inte- · Annual availability of forest fuels. grated. In general, the production cost of forestry resi- · Fuel mix (residues, small trees, stumps). dues largely depends on the following criteria: · Transport distances in the forest or the on-road network. · Comminution type. · Location of plant (center of a town or in the subur- · Transportation distance. ban area). · Storage and drying. · Size of plant yard (storage). · Degree of mechanization. · Type of biomass energy plant (power only, heat · Steepness of the terrain. only, CHP). · Type and size of the machines used. · Dominant technology to produce chips. · Labor costs in the country. · Need for GIS-based resource availability and cost analysis. When a number of harvesting sites for forestry res- idues are available, it is important to select the site 40 Biomass Supply from Forestry Residues with the best characteristics from the perspective of · Short terrain transport distance. biomass supply. Characteristics of a good harvesting · A spacious roadside storage area for long distance site for forestry residues include the following: transport. · Many tree species with a large portion of foliage and Hauling distances to the energy plant help determine branches, for example, spruce (Picea abies), which which harvesting chain is the most economic. Hauling allows for a good recovery rate and productivity. distances should be kept within reasonable limits. If · Enough fertile soils. distances become too long to provide sufficient bio- · A sufficiently large felling site or a concentration of mass to a dedicated large-scale biomass energy plant, stands. it may be wiser to opt for a smaller energy plant or · Easily traversed, well-bearing ground. aim at the cofiring of biomass. · No undergrowth to hinder forestry. 41 6. Managing the Biomass Fuel Supply 6.1 Organizing the Biomass Fuel Supply For various reasons, the price, quantity, and specifica- tions of actual fuel supplies may not match what was A biomass-fired power plant needs biomass fuel. To contracted. It is therefore important for the biomass operate continuously, and in particular at the time of power plant to develop a strategy to mitigate fuel sup- initial plant start-up, the power plant will need a stock ply irregularities and risks. Section 6.4 describes how of biomass fuel. To replenish the stock, biomass fuel a fuel supply risk matrix can be used to develop miti- will need to be supplied to the plant regularly. For a gation strategies. large power plant, dozens of trucks or several train- loads may be needed on a daily basis. 6.2 Biomass Fuel Contracting To ensure the efficient operation of a biomass fuel sup- At the plant planning stage, Chinese biomass-fired ply chain, the fuel supplies need to be well organized power plants should preferably sign long-term supply during the planning stage, as well as the operational contracts to secure the large volumes of fuel required stage of the power plant. Efficient organization is nec- for plant operation. Biomass fuel contracting refers to essary to be able to procure biomass fuel at acceptable all activities aimed at securing the supply of biomass costs, so that the power plant can operate profitably. fuel of the right quality, in the right way, in the right Furthermore, any entity providing investment capi- quantities, at the right time, and at the right price. tal for a bioenergy plant will usually require that fuel supply contracts be in place before project funding is The main issues to cover in a biomass fuel supply con- approved. tract are fuel quantity, fuel quality (including quality standards and specifications), fuel pricing, and fuel There is no standard recipe for how best to organize delivery. Other important terms usually covered in and structure the biomass fuel supply chain, given that biomass fuel supply contracts are guarantees, sam- it depends on many factors. However, it is possible to pling, payment conditions, an escape provision for draw up an overview of important fuel supply con- conditions beyond the control of either buyer or seller, siderations. This chapter will address some of these penalties for noncompliance, and other terms and issue. conditions. Section 6.2 presents the main aspects of biomass fuel Depending on the biomass power plant's preferences, contracting. These will need careful consideration at it may seek to contract for feedstock from a single sup- the planning stage. Section 6.3 discusses activities at plier, or a few or multiple suppliers. It is recommended the power station (for example, sampling, exclusion, to enter into contracts with at least a few different and monitoring) aimed at ensuring that the biomass fuel suppliers to avoid temporary shutdown if the bio- fuel received meets the supply contract requirements. mass supply from a dominant supplier is interrupted These activities need attention at the operational stage. or becoming too expensive. For example, the 12 MW This section also describes a method for fuel inspec- Henan province biomass power plant has chosen to tion and quality control. work with many small-scale fuel brokers to prevent a 42 Managing the Biomass Fuel Supply large fuel supplier or broker from controlling the fuel Thus, the first step is to determine which type(s) of price. biomass to fire in the power plants, and to assess the approximate amount of each biomass type needed per If the power plant decides to deal with a few preferred period of time (for example, daily, weekly, monthly, or suppliers, a thorough assessment of their capacity annually). It is understood that Chinese power plants and reliability is warranted. Such assessments are less are usually designed to be sufficiently flexible, and important (and probably not even feasible) when the they already have the required operational permits in power plant deals with a multitude of suppliers. place to allow a blend or mix of different types of bio- mass to be fired. To meet the power plant's preference to deal with a limited number of contract partners, individual fuel Which biomass fuel is actually contracted for does not owners (land owners or crop growers) can band depend so much on the availability of the biomass fuel together in a cooperative and work through the coop- alone, but on its availability at the right price. This erative to contract with the power plant. Alternatively, concept is also known as contractability. Important a private fuel supplier can operate as an intermediary factors that help determine the availability of a spe- between landowners and growers on one side and the cific type of biomass from a given supplier at a given power plant on the other. time include the following: Annex 8 presents a sample biomass fuel supply con- · The supply radius considered. tract with some guidance notes, developed by the Car- · Competing uses (applications). bon Trust (Carbon Trust 2005b). · Competition among suppliers. · Seasonal patterns (crop growing/harvesting seasons). 6.2.1 Biomass Fuel Quantity · Terrain conditions (access may be restricted during The amount of fuel a biomass power plant requires is winter or rainy season). directly linked to the plant's capacity, the number of operational hours, the load factor, and the conversion To the extent that these factors are not covered in the efficiency. Other important factors include the type(s) biomass resource assessment, they should be taken of biomass used, its bulk and energy density, moisture into consideration before the power plant signs any content, and calorific value.12 Even for the same type contracts with its fuel suppliers. of biomass (wood), there can be considerable fluctua- tions in these parameters.13 6.2.2 Biomass Fuel Quality The quality of the biomass feedstock has a large influ- ence on the performance of the combustion process 12. See chapter 2 for more details on relevant fuel character- and the equipment life span. Smaller plants especially istics. require high-quality biomass fuel. For that reason, it is 13. Although the energy content of wood by weight varies very important to include quality requirements in the very little between different timber species, the density varies biomass fuel supply contract. significantly. Therefore, if the end user is purchasing biomass by weight, the species of timber should not matter (although clearly the moisture content of the biomass will). However, if To help the biomass power plants formulate quality purchasing biomass by volume, the energy content will be de- requirements, it may be practical to use fuel standards. pendent upon the timber species. For example, the typical calo- rific value of softwood chips at 30 percent moisture content is For example, solid biomass standards were introduced 0.70 MWh/m3, compared with 1.02 MWh/m3 for hardwood in Europe and in individual European countries for chips at 30 percent moisture content. In addition, the bulk den- biomass fuel to become a commodity with common sity will vary considerably, resulting in a highly variable volume definitions, common methods, and a clear classifica- expansion from 1 m3 of solid wood to anywhere between 2 and 5.5 times the original volume when chipped (Carbon Trust tion system. At the European level, the CEN devel- 2005a). See annex 9. oped standards to describe all forms of solid biomass, 43 Fuel Supply Handbook for Biomass-Fired Power Projects including wood chips, wood pellets and briquettes, 2007a, 2007b). An example of cost structures for dif- logs, sawdust, and straw bales. More information on ferent forestry residue fuels in Finland is shown in fig- these CEN biomass fuel standards and specifications ure 6.1. is presented in annex 2. For all biomass fuels, the moisture content is a very When supplied fuel is not in compliance with the speci- important quality specification. Dry biomass has a fications, it may be rejected by the buyer or reduced to greater specific energy content than wet biomass. For a price that is agreeable to both buyer and seller. that reason, it is recommended during biomass con- tracting to reflect moisture content in the biomass 6.2.3 Biomass Fuel Pricing pricing wherever possible. Van Loo and Koppejan To ensure that the biomass power plant is capable of (2008) mention three different alternatives for pricing operating economically in the long term, it is crucial fuel based on the delivered energy content. Details are that biomass fuel is always available at an acceptable presented in annex 10. price. Biomass power plants should put a high prior- ity on contracting for and securing low-cost feedstock. The increased demand for, and use of, agricultural The price that a power plant needs to pay for biomass and forestry residues for energy generation (for feedstock depends on many factors, including fuel type example, as a result of a new bioenergy plant being (species), quality, volumes from suppliers, reliability, built in the same collection area) can lead to higher local market conditions, availability (which depends feedstock prices, first, for the raw material itself, as a on such factors as the season, the weather, and market direct result of increased competition for its use, and competition), and transportation distances and costs. second, for the transportation of the raw material, Because so many different factors influence the final because it may need to be obtained from more difficult biomass fuel price, it is recommended to determine and distant stands. Two examples can illustrate this benchmark prices and to carry out market surveys at upward price trend. In Finland, the price for logging regular intervals (data collection and analysis on avail- residue chips dropped in the 1980s and 1990s, but ability of residues and demand by current and future increased in the early years of this century, partly as a competitors). result of increased demand. In the Netherlands, highly competitive uses for wheat straw (soil conditioning, The final price can consist of a fixed price negotiated cattle breeding, horticulture, bedding material for with the fuel supplier or an initial price based on the tulip bulbs) forced the price up to more than 100 full costs of supplying biomass to the power plant with per ton. The development and implementation of new a price index. The initial price then changes over time bioenergy technologies can further increase the mar- by periodically applying the agreed-on indexation ket competition for agricultural and forestry residues. (Carbon Trust 2005b). Examples include second-generation ethanol produc- tion or thermal "biomass-to-liquid" production. To negotiate effectively, it is important for a biomass plant owner to understand the cost structure of the 6.2.4 Other Supply Contract Considerations biomass fuel. In the highly developed Danish straw- Seasonal Restrictions for-energy market and the Finnish and Swedish wood- Specific fuels, such as agricultural and forestry residues, for-energy markets, cost structure surveys are done may only be available in specific periods or under cer- every few years. DTI (2007b) presents a cost structure tain field conditions. In Scandinavia, forest operations for wheat straw (production of big bales) in Denmark come to a halt during part of the year as a result of that covers the value of wheat straw in the field (5.00 limited terrain accessibility. For agricultural residues, per ton); turning or raking (5.00 per ton); baling the harvesting window is typically limited to approxi- (19.00 per ton); loading, transport, unloading (6.00 mately two months. To address these seasonal restric- per ton); and storing at the farm (14.00 per ton) (DTI tions, it is important to construct biomass storage 44 Managing the Biomass Fuel Supply Figure 6.1 Cost Structures of Different Forestry Residues Fuels in Finland 40 35 delivery cost terminal cost 30 The cost gap = transport cost at the plant, /m3 25 felling cost chipping in-woods chipping 20 harwarder logging 15 forwarding 10 bundling felling and bunching 5 other cost 0 feller feller harwarder harwarder lumberjack lumberjack harvester harvester chipping chipping loose logging buncher buncher and and and and and and at in logging residue and and chipping at chipping at chipping at chipping at chipping at chipping at roadside terrain residues bundles chipping at crushing at RS. Whole PP. Whole RS. Whole PP. Whole RS. Delimbed terminal. storage RS. Whole PP. Whole trees trees trees trees trees Delimbed trees trees trees Small trees from early thinnings Logging residues Source: Laitila 2005. Note: RS = Roadside; PP = Power plant. A harwarder is a combination harvester and forwarder. capacity and to build up a sufficiently large fuel stock shutdown in the event of possible biomass fuel supply (at the biomass power plant or elsewhere in the supply interruptions, a biomass power plant should always chain). In addition, the biomass power plant may try, maintain a fuel buffer stock. whenever possible, to arrange planting and collection schedules with growers and forest owners. This allows Contract Duration better planning of delivery dates and supply quantities. Biomass-fired power plants generally prefer long-term When high-quality straw, for example, is available at a contracts for biomass fuel supply because financing certain time (even within a common straw harvesting agencies demand security of income. However, farm- window of two months), less straw has to be stored ers and landowners prefer a balance between security during the season, resulting in lower storage costs. of income (long-term contract) and flexibility. Initial Fuel Stock Build Up 6.3 Biomass Fuel Supply Control A special situation arises at initial plant start-up. The biomass fuel needed for initial operation needs 6.3.1 Introduction to Fuel Quality Control Measures to be contracted for and accumulated in the months At the plant operational stage, many activities need before the power plant starts operating at full scale. to be carried out at the power station to ensure that This requires early fuel contracting and construction the biomass fuel received meets the supply contract of effective fireproof and rainproof storage, as well as requirements. Such activities include transportation sufficient working capital to pay for these fuel sup- outside the plant; fuel inspection and quality control plies and facilities. To minimize the risk of temporary inside the plant; confirmation and determination of 45 Fuel Supply Handbook for Biomass-Fired Power Projects the fuel price upon arrival at the plant; management · Staff training and management: At present, about of the fuel loading, transportation, and storage inside 50 percent of the staff are involved in biomass fuel the plant; and staff training and management. Each supply in biomass-fired power generation plants subsystem should coordinate well with the others to in China. They play an important role in the effi- ensure fuel supply and reduce risks. ciency of fuel supply and cost control for power generation. Relevant tasks include the following (CECIC 2009a): 6.3.2 Quality Management for Fuel Supply Control · Fuel transportation system outside the plant: This To ensure that the delivered biomass complies with mainly includes the construction and maintenance the quality standards and specifications in the bio- of roads outside the power plant, selection and mass fuel supply contract, fuel inspection and quality improvement of loading systems and transporta- control are necessary throughout the biomass sup- tion, and communication and coordination with ply chain. All operators in the biomass supply chain the local transportation department. At present, should apply quality control measures. Especially at the loading system and transportation are usually the gate of the biomass-fired power plant where the managed by biomass fuel suppliers themselves, and physical reception of the fuel takes place, sampling, the power plant takes charge of road maintenance exclusion, and monitoring of the fuel is required. and coordination with the local transportation department. A possible tool for controlling fuel quality along the · Inspection and quality control system inside the plant: entire supply chain is a quality management (QM) sys- Fuel quality control is the key step for a biomass- tem. Langheinrich and Kaltschmitt (2006) developed fired power generation plant. It is necessary to a six-step methodology for designing a QM system for identify the method of fuel evaluation according to solid biomass supply (see figure 6.2). They recommend the requirements of the biomass boilers and other setting out the practical implementation of the QM equipment, and then to ascertain the fuel purchase system in an operator manual, which will help keep price. It is important to continually improve qual- all process steps and interactions under control. At a ity control and evaluation-record management. minimum, the manual should cover the following: An example of the sampling and handling process applied to wood fuels in Finland is presented in · Documentation of origin (traceability of raw annex 11. material). · Fuel price upon arrival at the plant: The price fluctu- · Steps in the process chain, critical control points ates according to fuel type, season, and quality, as (CCPs), criteria and methods to ensure appropri- well as the relationship between fuel demand and ate control at CCPs, and nonconforming products supply. It is necessary to establish a scientific and (production requirements). feasible price and fuel purchase method to encour- · Description of transport, handling, and storage. age rural households to collect and transport bio- · Quality declaration and labeling (final production mass fuel to the plant. specification). · Loading, transportation, and storage system inside the plant: A 25 MW biomass power generation project The methodology is described in more detail in needs more than 500 tons of biomass fuel every annex 12. day. It is very important to ensure sufficient fuel supply by effective fuel loading, and by selecting Quality Assurance (QA) measures should (a) be sim- the suitable feeding system, fuel storage amount, ple to operate, (b) not cause undue bureaucracy, and and pattern. In addition, it is necessary to make (c) offer savings in costs to both producers and users. sure that road layout and construction inside the The application of QA measures enables the reduc- plant, as well as the fire and water prevention sys- tion of costly quality control measures and will lead tems, are designed and constructed well. to lower failure costs. 46 Managing the Biomass Fuel Supply Figure 6.2 Methodology to Apply and Implement Quality Assurance 3. 2. 4. 5. 6. 1. Analysis of Determination Identification Selection of Routines for Description of quality of customer of Critical appropriate non-conforming process chain influencing requirements Control Points QA measures materials factors Elaboration of a process (site)-specific manual Sources: BTG; Drohm Design & Marketing based on Langheinrich and Kaltschmitt 2006. Note: QA = Quality assurance. Quality Control (QC) includes the selection and appli- each percentage point that the moisture content is less cation of appropriate sampling and sample-reduction than 13 percent, but only to 10 percent. No further techniques, as well as test methods. QC is important price adjustments are made if the moisture content is for assessing the properties of the fuel that is delivered, less than 10 percent (DTI 2007b). but it does not directly affect the quality of a product. The application of sample and test methods is expen- 6.3.4 Case Study: Quality Management of Forestry sive, so they should be used carefully and not as a mat- Residues in Finland ter of routine (Langheinrich and Kaltschmitt 2006). In the highly developed wood-for-energy market in central Finland, fuel is paid for on the basis of its 6.3.3 Case Study: Quality Management of Agricultural energy content, and fuel inspection at cogeneration Residues in Denmark plants often focuses on just two aspects: moisture In the highly developed Danish straw-for-energy content and net calorific value. While unloading the market, the presence of mold in the straw is mostly forestry residues, the truck driver takes fuel samples ascertained by visual inspection. To measure weight, manually, using special sample buckets. These buckets the larger power plants and CHPs use automatic mea- have a cylinder, with a diameter of about 15 cm, in the surement systems, while the smaller district heating nose of an arm. According to the standard, 4­6 sam- plants measure manually by unloading. To determine ples should be taken from one truck-trailer load. In the moisture content, a measuring spear is inserted in practice, sometimes just one sample is taken from the the straw bales. Typically, in one load (16­24 bales), truck and another from the trailer. This causes inaccu- the spear is inserted in at least four bales in differ- racy in determining single-load properties, but when ent positions of the bale. The biomass price is deter- the annual volume is large, occasional faults will even mined based on an average of the moisture content out over larger numbers of loads. Single fuel samples measurements. are combined and, from the combined sample, mois- ture content is determined daily for each supplier. If the average moisture content is more than 13 per- Calorific value is tested less frequently, for instance, cent, the payable load is reduced by 2 percent for each once a month. Particle size is determined only when percentage point over 13 percent. Thus, the price for new machines or raw materials are introduced or as the load is reduced. If the average moisture content is a random control (DTI 2007a). To measure weight, more than 23 percent for two bales, the load will be weighbridges are used. Energy content is calculated rejected. If the average moisture content is less than 13 according to the European Technical Standard CEN/ percent, the payable load is increased by 2 percent for TS 15234. 47 Fuel Supply Handbook for Biomass-Fired Power Projects 6.4 Mitigation Strategies for Managing · Cardinal scales identify the probability and impact Supply Risks on a numerical value, from .01 (very low) to 1.0 (certain). In addition to organizing efficient fuel supply under · Ordinal scales identify and rank the risks from very normal conditions, the biomass power plant should high to very unlikely. also develop an emergency system to address potential disruptions in the fuel supply. Disruptions can result Each identified risk is fed into a matrix, which maps from different causes, and which of the large number out the risk (cause and consequences), its probability, of supply risks are most pertinent for a given biomass and its possible impact. The risks with higher prob- power plant is situation-specific. It is important for a ability and impact are a more serious threat to the bio- biomass plant owner or operator to make plant-spe- mass power project than risks with lower impact and cific risk assessments, that is, carefully examine what probability. could cause disruptions in the biomass fuel supply and identify suitable mitigation measures, so that the focus There are many potential sources of risk that can can be placed on the risks that have the highest prob- affect the continuous supply of affordable feedstock ability, or the greatest impact, or both. to the power plant (Thornley, personal communica- tion, 2009).14 A survey of the relevant literature and A biomass fuel supply risk matrix is a suitable tool to Thornley's own long-term experience developing bio- determine key risks and mitigation options. Develop- energy projects around the world confirm that manag- ing a risk matrix consists of the following steps: ing fuel supply risks is a crucial factor for efficient and economic plant operation. Annex 13 gives an exam- · Cause: Identify the risks along the biomass fuel sup- ple. The matrix is only intended as an example, show- ply chain that can cause supply disruptions. During ing some common supply risks and mitigation factors. the risk-identification process, identify all possible Without a detailed field study of the experience at sev- fuel supply risks, irrespective of their probability eral Chinese power plants, it is not possible to accu- and impact. Risks are undesirable events that hin- rately identify and rank the most relevant supply risks. der the achievement of project objectives. It is recommended that the power plant develop a fuel · Potential impact (event): Identify the consequences supply risk matrix at the project planning stage. With to the biomass fuel supply if the event occurs. the assistance of a biomass supply expert, the supply · Risk probability classification: risks and the most suitable mitigation strategies can · Risk probability (low, moderate, high) is the be determined. likelihood that a risk event occurs. · Risk impact (low, moderate, high) is the conse- Experience around the world shows that Chinese bio- quences that the risk event will have on achiev- mass power plants are not unique in facing problems ing project objectives. managing biomass fuel supply risks. For example, · Remedies: Develop solutions to minimize or elimi- power utilities in the United States (Midwest, South- nate the risks (mitigation strategies). Examples of east, and Texas) that use woody biomass as a fuel mitigation strategies include biomass contracting, for power generation are facing the gap between the fuel inspection (sampling, exclusion, and monitor- supply needs of power utilities and the practices and ing), engineering design (dual feed system, buffer capabilities of the existing woody biomass suppliers. capacity, and storage), and the availability of alter- As stated above, biomass fuel supply specialists can native biomass fuels. help identify key physical delivery risks and mitigation To rank the risks, two possible approaches can be 14. Dr. Patricia Thornley, Tyndall Centre for Climate Change adopted: Research, University of Manchester. Throughout her academic career, Dr. Thornley has identified hundreds of risk factors for biomass power plants. 48 Managing the Biomass Fuel Supply strategies, as well as assign prices to risk-management the installed energy system. Biomass fuel not in com- challenges and opportunities. These topics were cov- pliance with the specifications in the contract may be ered at a web seminar organized by Electric Utility rejected or the fuel price may be reduced. Consultants Inc.15 To negotiate for fuel supplies effectively, it is impor- tant for a biomass plant owner to understand the cost 6.5 Conclusions and Recommendations structure of the biomass fuel. It is recommended that It is recommended that power plants carefully select the moisture content be reflected in the biomass price, biomass fuel suppliers and develop long-term relation- because it is related to the calorific value of the fuel. ships and sign long-term supply contracts with the preferred suppliers. It is recommended to determine benchmark biomass fuel prices and to carry out market surveys at regu- Long-term contracts with few or multiple fuel sup- lar intervals (data collection and analysis on residues pliers (or brokers) help to reduce biomass supply availability and the demand of current and future risks. Farmers and landowners often consider a bal- competitors). The increased demand for, and use of, ance between security of income (long-term contracts) agricultural and forestry residues for energy genera- and flexibility to be important, and they may prefer tion can lead to higher feedstock prices. shorter-term contracts. In addition to organizing efficient fuel supply under The practical involvement of a biomass-fired power normal conditions, the biomass power plant should plant itself in fuel supply starts at the power plant gate also develop an emergency system to address poten- only if the fuel supply is fully contracted to a fuel bro- tial disruptions in the fuel supply. Managing fuel sup- ker or other external entity. ply risks is a crucial factor for efficient and economic plant operation. To manage physical delivery risks, it The biomass power plant should have a fuel stock is recommended not to depend on a single type of bio- available at all times. For large-scale power plants, as mass fuel. in China, this will require several fuel deliveries per day. It is important to design a power plant with some The power plant should assess fuel supply risks, that fuel flexibility and to build enough storage capac- is, examine carefully what could cause disruptions in ity to allow for scheduled (for example, the Chinese the biomass fuel supply and identify suitable mitiga- New Year break) and unexpected interruptions in fuel tion measures. Priority should be given to the risks supply. that have the highest probability and/or the greatest impact. To help ensure year-around availability of biomass at the plant, the power plant owner or operator can A biomass fuel supply risk matrix is a suitable tool for adopt several approaches. Options include arranging determining key biomass fuel supply risks and mitiga- planting schemes with growers and forest owners, tion options. A biomass supply expert can help the constructing sufficient storage capacity for continu- power plant determine supply risks and the most suit- ous operation, and fixing schedules for biomass fuel able mitigation strategies. deliveries. It is recommended that investors use a tool for manag- Fuel quality standards and specifications should be ing the biomass fuel supply, for example, a QM sys- included in the contract to match the fuel supply with tem, and to document practical implementation steps in the form of a manual that can serve as a tool for 15. Web seminar entitled Managing Supply Risks of Woody each operator active in the supply chain. Biomass for Power Generation, held October 16, 2009. 49 Fuel Supply Handbook for Biomass-Fired Power Projects To manage price risks, an interesting option is to offer power plant. When the biofuel supplier has a financial the preferred biomass supplier a financial stake in the interest in the power plant's performance, the chance power plant. 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Where the availability of biomass from use: residues is limited, additional biomass can be obtained from the cultivation of dedicated energy crops. This · Experience from Sweden shows that, if located, annex briefly discusses the state of the cultivation of designed, and managed wisely, energy crop planta- dedicated energy crops, referred to as "energy plan- tions can, besides producing renewable energy, also tations," and their contribution to biomass fuel sup- generate local environmental benefits. Examples of ply. Both short-rotation woody crops (SRWC), such such multifunctional bioenergy systems are Salix as willows and poplars, and herbaceous energy crops, L. plantations leading to soil carbon accumulation, such as Miscanthus and switchgrass, are potential bio- increased soil fertility, reduced nutrient leaching, mass sources. and improved hunting potential, representing more general benefits. Another category of plantations The establishment of energy plantations in Europe in is those designed for dedicated environmental ser- the 1990s was driven by the implementation of a com- vices, such as shelter belts for the prevention of soil prehensive support system for the agricultural sector. erosion, plantations for the removal of cadmium In some EU countries, energy crops were cultivated from contaminated arable land (phytoextraction), on demonstration fields, for example, in Greece (sor- and vegetation filters for the treatment of nutri- ghum, eucalyptus), Germany (Miscanthus), and Fin- ent-rich, polluted water (van Loo and Koppejan land (reed canary grass). In most of the then 15 EU 2008). member states, energy crop cultivation was limited to · The market valuation of biomass feedstocks can a few field trials. Commercial cultivation of woody internalize environmental benefits, such as carbon energy crops developed only in Sweden, where com- credits or reduced gas emissions. mercial willow plantations covered 15,000­17,000 ha. The European experience is described in more The relative competitiveness of SRWC for biomass detail below. power production will still be dictated by local con- ditions and will likely vary from region to region. In Worldwide, thousands of hectares of commercial plan- the long term, yield improvements and more-efficient tations of SRWC, such as willow, poplar, eucalyptus, harvest technologies are likely to play a bigger role in and southern pine, exist. These plantations provide reducing SRWC unit costs. valuable information about yields, propagation tech- niques, variety development, and best management With regard to herbaceous (grassy) energy crops, practices. Recent research in the United States shows experience gained to date is relatively limited. In the that the economics of SRWC biomass for bioenergy United States switchgrass and in Europe Miscanthus use are not yet favorable compared with non-energy have been tested on a relatively large scale. Both basic uses, and that SRWC fuelwood is not competitive with and applied research is needed, not only on yield and coal for power production, the dominant fossil fuel in management, but also on the conditions for their suc- U.S. and Chinese electric power generation (Graham cessful adoption. Besides profitability, other adoption 1995). factors include adaptability of energy crops to existing 55 Fuel Supply Handbook for Biomass-Fired Power Projects farming practices, machinery, time allocation, and the European Miscanthus Network. Reed canary grass farming know-how. (RCG) is native to Sweden, as well as many other parts of northern Europe. Several thousand ha of RCG have been established in Sweden, although very little of the European Experience Growing Woody grass is used for energy. In Finland, about 50 ha have and Grassy Energy Crops been established. Small research plots have been estab- Luger (2002) presents an overview of energy cropping lished in Denmark, Germany, Ireland, and the United experience in Europe in the 1990s. His article covers Kingdom. Cardoon (Cynara cardunculus) is a peren- woody crops, herbaceous crops, and oil seed crops. nial thistle-like plant that seems to be well adapted to For the first two categories, discussed below, the area dry Mediterranean conditions where most precipita- under cultivation since his overview was published tion occurs during the winter season. In Spain, about may not have changed dramatically. 50 ha of experimental fields have been established. Within the Cynara network, green Cynara forage cut- With regard to woody crops, willow (Salix sp.) is tings were tested during winter in Greece, Italy, and grown mainly in the northern parts of the EU. In Portugal. Sorghum (Sorghum bicolor) is an annual C4 Sweden, some 17,000 ha of willow are grown. The crop of tropical origin. It is, therefore, mainly adapted combined contribution of other EU willow-growing to southern Europe. Both sweet sorghum and fiber countries, in particular, Denmark, Finland, Ireland, sorghum have been tested for energy production. Bel- the Netherlands, and the United Kingdom, was on the gium, France (about 15 ha), Greece, Italy, Portugal, order of 1,000 ha. Poplar (Populus sp.) can be grown and Spain grow sorghum. Hemp (Cannabis sativa) has in warmer climates than willow. In some countries, a long tradition as a fiber crop, but the use of hemp such as Austria, Belgium, Ireland, Germany, and the for energy is a new idea. In the Netherlands, hemp United Kingdom, both willow and poplar are grown. is used for pulp production. Approximately 5 ha are In the Netherlands, about 32,000 ha of poplar have grown for energy uses. An area of 1,000 ha is grown been established, but not for energy purposes. In commercially for fiber use. In Austria, 160 ha of hemp France, about 350 ha have been established and used were grown for seed and fiber use (Luger 2002). for pulp production. The largest European areas of Eucalypt (Eucalyptus sp.) in short rotation have been Luger (2002) concludes that a few energy crops have established in Portugal, where approximately 500,000 exceeded the level of research, development, and dem- ha are grown for pulp production. In France, a total onstration, and have become commercialized. These of about 500 ha of eucalypts are planted for pulp pro- examples exist because of the political and financial duction, and in Greece and Italy, only small test plots support given by some countries, and they have pro- of a few hectares for research have been established. vided valuable information on the future demands for the implementation of energy crops in European With regard to herbaceous crops, Miscanthus sp. was agriculture. The best-known example of large-scale introduced to Europe as an ornamental plant. As a commercial energy crop production for biomass heat C4 perennial grass, it is better adapted to warmer and power generation is the cultivation of willow in climates.16 In Denmark about 30 ha are established, Sweden. while in Germany there are about 100 ha, and in Aus- tria and France a few hectares. In Belgium, Greece, Economic calculations show basic costs of production Ireland, Italy, Portugal, Spain, and the United King- and delivery to a power plant to be in the range of dom, small research plots were established as part of 34­86/odt (caution: 1996 data). The Swedish calcu- lation of 59/odt for willow is the most well founded. 16. Agricultural experts make a distinction between C3 and These costs compare favorably with market prices pre- C4 plants, depending on the length of the growing season. A vailing at the time for biomass residues (such as forest C4 plant is a plant that produces the 4-carbon compound ox- alocethanoic (oxaloacetic) acid as the first stage of photosyn- wood chips), which were on the order of 32­68/odt thesis. in Sweden and about 80/odt in Denmark. The mean 56 Annex 1: International Experience with Growing Energy Crops market price of straw in Denmark is about 70/odt. Wang and Xiao (2008) report that in northern China, The market price of fossil fuels (in /GJ) is lower than 600,000 ha of fuelwood forests are planted annually. these biomass prices (Luger 2002). An estimated 100 million tons per year of woody mate- rial can be collected. According to the State Forestry The above cost ranges indicate that basic production Administration's National Energy Forest Construc- costs of energy crops in some cases can compete with tion Plan, more than 10 million mu of demonstration existing biomass based on market prices, and with energy forests will be built up during the 11th Five- fossil fuels, but only if land rentals and profits for the Year Plan period (2006­10). These forests will provide farmers are not included in the calculations. significant potential for future energy generation. In 2005, total forested area in China stood at 175 mil- Chinese Experience Growing Woody lion ha, of which 68 percent was natural forest (121 and Grassy Energy Crops million ha) and 32 percent was planted forest (54 mil- Wang and Xiao (2008) present a list of species suit- lion ha). The forest stock is unevenly distributed and able for fuelwood production. In China, suitable spe- mostly concentrated in the five principal forest regions, cies include the following: which account for 90 percent of total forest stand vol- ume. Seventy percent of existing forest is in middle and · Eucalypt, Cassia siamea, birch, and sawtooth oak young age. in the high mountainous regions of Sichuan and Yunnan provinces. Since the mid-1990s, China has pursued an active · Quercus acutissima, Quercus variabilis, alder, Cori- afforestation policy at all government levels. With an aria sinica, and acacia in the mountainous regions annual afforestation rate of approximately 3­4 mil- of Sichuan and Shaanxi. lion ha, the national forest coverage rate is expected · Sawtooth oak, eucalypt, Acacia mearnsii, Zenia to increase from 18.21 percent in 2005 to 20 percent insignis, and Schima superba in the low mountain- in 2010. In addition to expansion of the coverage rate, ous regions of south and central Yunnan. China strives to improve the quality of its forests, · Sawtooth oak, Pinus massoniana, Platycarya stro- enhance carbon fixation capacity per unit of forest bilacea, acacia, Lespedeza, Choerospondias axillaris area, moderately increase the usage and service life of in the low mountainous and hilly regions of north- forest lumber, and strengthen forest products' carbon west Zhejiang, south Anhui, and northeast Jiangxi. stock capacity. · Acacia dealbata, Castanopsis luminifera, Pinus massoniana, eucalypt, Zenia insignis, and Schima Dr. Chunfeng Wang, Deputy Director General of the superba in the mountainous regions of south State Forestry Administration, envisages that by 2010, Jiangxi, southwest Hubei, southeast Guizhou, cen- up to 300 million tons of forest biomass can be used tral and northern Guangdong, and Guangxi. as a substitute for coal for energy generation (Wang 2009). 57 Annex 2: Fuel Standards and Specifications Fuel standards have been introduced so that biomass be provided). As well as the physical and chemical can become a commodity fuel with common defini- characteristics of the fuel, CEN/TC 335 also requires tions, common methods, and a clear classification information on the source of the material. system. It is important that the fuel is fit for purpose (proper match between fuel supply and energy system) The CEN/TC 335 standards are intended to be uni- and delivered according to a quality standard and versal standards. The European solid biofuel stan- specification. Fuel quality standards also encourage dards build on national solid biofuel standards that the uptake of biomass fuels through consumer confi- were already in place in, for example, Austria, Ger- dence (Richards and Maunder 2008). many, and Sweden (ÖNORM, DIN, and SS standards, respectively). In Europe, the European Committee for Standardiza- tion (CEN) formed a technical committee (CEN/TC Standards 335--Solid Biomass) to develop standards to describe all forms of solid biomass within the biomass-biofuel When investing in a biomass-fired power plant, it field (figure A2.1), including wood chips, wood pellets is important to know that most types of conversion and briquettes, logs, sawdust, and straw bales. CEN/ equipment work effectively only with select types and TC 335 allows all relevant properties of the fuel to be forms of biomass fuel. As mentioned before, there are described, and includes both normative information different sets of standards. Regardless of which set of (must be provided) and informative information (may standards is applied, it is important to work closely Figure A2.1 CEN/TC 335 Within the Biomass-Biofuel-Bioenergy Field Biofuel Biomass Bioenergy Solid biofuel Production/preparation CEN/TC 335 Conversion Liquid and gaseous biofuel Non-fuels Sources: BTG; Drohm Design & Marketing based on the work of CEN/TC 335. 58 Annex 2: Fuel Standards and Specifications with both fuel supplier and system installer to ensure · Supplier (body or enterprise), including contact that the fuel purchased is suitable for the system, that information. the fuel supplier undertakes to deliver a consistent · A reference stating compliance to the CEN/TS quality of fuel, and that the fuel can be stored and 15234. handled at the site correctly (Carbon Trust 2005a). · Origin and source (prEN 14961-1). · Traded form (prEN 14961-1 or other parts). · Normative properties. Specification and Classes · Chemical treatment if chemically treated biomass The classification of biomass is based on origin and is traded. source, major traded types, and properties. Classifi- · Signature (authorized person), name, date, and cation is useful for boiler and burner manufacturers place. to select property classes for their products. The clas- · The fuel quality declaration can be approved elec- sification can be marked on the product if packaged, tronically (signature and date can be approved by and for bulk material, a fuel quality declaration can be signing the waybill or stamping the packages). used (CEN/TS 15234) (see figure A2.2). An example of a quality declaration according to Part According to Alakangas (2008), the minimum require- 1­Bulk delivery is shown in figure A2.3. ments for a fuel quality declaration are as follows: Figure A2.2 Example of Classification Based on Origin and Source, Major Traded Form, and Properties (Tables with property grades in prEN 14961-1) Traded form Origin/source (for example, pellet) Fuel production Biomass Solid biofuel Bioenergy use Conversion Origin/source Documentation Quality of origin declaration (Table 1 in EN14961-1) (prEN 15234) Fuel Quality Assurance (prEN 15234 upgrading ongoing) Sources: BTG; Drohm Design & Marketing based on Alakangas 2008. 59 Fuel Supply Handbook for Biomass-Fired Power Projects Figure A2.3 Example of a Fuel Quality Declaration Used for Bulk Delivery EN 14961--Part 1 Producer EAA Biofuels Pellet factory Jyväskylä, Finland Origin 1.2.1.2 (Sawdust, pine) Traded form Pellets Normative Dimensions D08 Moisture, w-% M 10 Ash, w-% dry A0.5 Mechanical durability, w-% pellets after DU97.5 Amount of fines, w-% (<3.15 mm) F1.0 Additives, w-% of pressing mass 0.5 w-% starch Bulk density, kg/m3 BD 650 Net calorific value as received, kWh/kg Q4.7 Sulphur, w-% dry basis 0.05 Informative Nitrogen, w-% dry basis N0.3 Chlorine, w-% dry basis C10.03 Sources: BTG; Drohm Design & Marketing based on Alakangas 2008. 60 Annex 3: Calculation of the Net Calorific Value at Different Bases and Energy Density as Received--EN 14961-1 D.1 The net calorific value of dry basis Note: [w(O)d + w(N)d] can be derived by subtract- ing from 100 (w-%) the percentages of ash, carbon, The net calorific value at a constant pressure for a dry hydrogen, and sulphur. sample (dry basis, in dry matter) is derived from the corresponding gross calorific value at a constant vol- ume according to Equation (EN 14918) (1) D.2 The net calorific value as received a) Calculation from dry basis qp,net,d = qv,gr,d ­ 212.2 × w(H)d ­ 0.8 × [w(O)d + w(N)d] (1) The net calorific value (at constant pressure) on as received (the moist biofuel) can be calculated on the where net calorific value of the dry basis according to Equa- tion (2). qp,net,d is the net calorific value for dry matter at a con- stant pressure in joules per gram(J/g) or kilojoules per kilogram (kJ/kg); qp,net,ar = qv,net,d × 100 ­ Mar ­ 0.024 43 × Mar (2) 100 qv,gr,d is the gross calorific value for dry matter in joules per gram(J/g) or kilojoules per kilogram (kJ/kg); where w(H)d is the hydrogen content, in percent- qp,net,ar is the net calorific value (at constant pressure) as age by mass, of the moisture-free (dry) biofuel received in megajoules per kilogram (MJ/kg); (including the hydrogen from the water of hydration of the mineral matter as well as the hydrogen in the qp,net,d is the net calorific value (at constant pressure) in biofuel substance); dry matter in megajoules per kilogram (MJ/kg); w(O)d is the oxygen content, in percentage by mass, of Mar is the moisture content as received [w-%]; the moisture-free biofuel; 0.024 43 is the correction factor of the enthalpy of w(N)d is the nitrogen content, in percentage by mass, of vaporization (constant pressure) for water (moisture) the moisture-free biofuel. at 25°C (in megajoules per kilogram (MJ/kg) per 1 w-% of moisture). For the calculation of the net calorific value as received using Equation (2) in D.2, the result from Equation b) Calculation from dry and ash-free basis (1) in joules per gram(J/g) or kilojoules per kilogram The net calorific value (at constant pressure) on as (kJ/kg), shall be divided by 1 000 to get the result in received (the moist biofuel) can be calculated from a megajoules per kilogram (MJ/kg). net calorific value of the dry and ash-free basis accord- ing to Equation (3). 61 Fuel Supply Handbook for Biomass-Fired Power Projects qp,net,ar = qp,net,daf × (100 ­ Ad) × 100 ­ Mar ­ 0.024 43 × Mar D.3 Energy density as received 100 100 (3) The wood fuels for small-scale heating plants and households are traded usually on a volume basis and where energy content (net calorific value) is informed often as megawatts hour (MWh) per bulk volume. Bulk den- qp,net,ar is the net calorific value (at constant pressure) sity and moisture content is measured or estimated. as received, in megajoules per kilogram (MJ/kg); The energy density as received can be calculated qp,net,daf is the net calorific value (at constant pressure) according to Equation (4). 1 ×q in dry and ash-free basis, in megajoules per kilogram Ear = p,net,ar × BDar (4) 3600 (MJ/kg); Mar is the moisture content as received (w-%); where qp,net,ar is the ash content in dry basis (w-%); Ear is the energy density of the biofuel as received, in megawatts hour per cubic meter (MWh/m3) of bulk 0,024 43 is the correction factor of the enthalpy of volume; vaporization (constant pressure) for water (moisture) at 25 °C (in megajoules per kilogram (MJ/kg) per 1 qp,net,ar is the net calorific value (at constant pressure) w-% of moisture). as received, in megajoules per kilogram (MJ/kg); In both the above cases a) and b), the calorific value BDar is the bulk density, that is, volume weight of the can be either determined for that particular lot or a biofuel as received, in kilograms per cubic meter (kg/ typical value can be used. m3) of bulk volume; 1 · If the ash content of the fuel is low and rather con- 3600 is the conversion factor for the energy units stant, the calculation can be based on the dry basis (megajoules (MJ) to megawatts hour (MWh)). equation with a typical value of qp,net, d; · If the ash content varies quite a lot (or is high) for The result shall be reported to the nearest 0.01 MWh/ the specific biofuel then using the equation for dry m3 of bulk volume. and ash-free basis with a typical value of qp,net,daf is preferable. The values of net calorific value and bulk density used in equations can be either measured or based on typi- The result shall be reported to the nearest 0.01 MJ/kg. cal values of biofuels. The typical net calorific values of solid biofuels are reported in Annex B of this Euro- pean Standard. 62 Annex 4: Types of Biomass Potential This annex is based on the work carried out by BTG usually expressed in joules of primary energy, but in the frame of the European BEE project (publication sometimes also in secondary energy carriers. forthcoming). Economic Potential Theoretical Potential The economic potential is the share of the technical The theoretical potential is the overall maximum potential that meets criteria of economic profitability amount of terrestrial biomass that can be considered within the given framework conditions. The economic theoretically available for bioenergy production within potential generally refers to secondary bioenergy car- fundamental biophysical limits. The theoretical poten- riers, although sometimes primary bioenergy is also tial is usually expressed in joules of primary energy, considered. that is, the energy contained in the raw, unprocessed biomass. Primary energy is converted into secondary Implementation Potential energy, such as electricity or liquid and gaseous fuels. For biomass from crops and forests, the theoretical The implementation potential is the fraction of the potential represents the maximum productivity under economic potential that can be implemented within theoretically optimal management taking into account a certain time frame and under concrete sociopoliti- limitations that result from temperature, solar radia- cal framework conditions, including economic, insti- tion, and rainfall. The theoretical potential for residues tutional, and social constraints and policy incentives. and waste equals the total amount that is produced. Studies that focus on feasibility or the economic, envi- ronmental, or social impacts of bioenergy policies relate to implementation potential. Technical Potential The technical potential is the fraction of the theoreti- Classifying biomass potential helps the reader to cal potential that is available under the anticipated understand the information presented. For instance, techno-structural framework conditions and with the some biomass types show high technical potential, but current technological possibilities, also taking into their economic potential is limited because of the high account spatial constraints from competition with costs of extraction and transport. Therefore, the type other land uses (food, feed, and fiber production), as of potential must be explicitly mentioned in every bio- well as ecological (such as nature reserves) and other mass resource assessment. nontechnical constraints. The technical potential is 63 Annex 5: Determination of Yield from Agricultural Crops and Residues The Biomass Assessment Handbook (Rosillo-Calle The crop residue index is determined in the field for and others 2006) describes a survey methodology for each crop and crop variety, and for each agro-ecolog- determining the availability of agricultural crops and ical region under consideration. It is very important residues. The methodology is briefly presented below. to state clearly whether the crop is in the processed or unprocessed state, for example, for rice, whether the Accurate estimates of the availability of crop residues husk is included in the crop weight. require good data on crop production by region or district. If these data are not available, a survey will To obtain accurate estimates of residue production, be necessary. A survey should include information on it is thus important to have good estimates of crop all uses for crop residues besides fuel (such as burning production by country, region, or district. This may in situ, mulching, animal feed, and house building), so entail undertaking surveys, especially in the subsis- that the amount available as fuel can be calculated. tence sector, to determine production of both crops and plant residues. If only general estimates of crop An assessment of agricultural residues should include residues are required, crop production figures may be the following steps: obtained from country statistics or UN bodies, such as the Food and Agriculture Organization of the United Define which types of biomass to include: It is important Nations (FAOSTAT). However, such statistics may be to consider data only on those agricultural crops and based on guesses when dealing with subsistence agri- residues that are used for fuel rather than the total cultural production, and hence, if accurate informa- biomass production on any site. tion is needed, field surveys may still be necessary. Obtain data on yields and stocks: For agricultural crops, Calculate economic and implementation potential: reliable information on yields and stocks, quantified The quantity of biomass from crop residues that is accessibility, calorific values, and storage and/or con- available for fuel is only a fraction of the technical version efficiencies must be accurately determined. A potential, because not all of it will be accessible at a study of the sociocultural behaviors of the inhabitants reasonable cost. Accessibility of crop residues depends of the project area will help to determine biomass use mainly on the location and the economic value of the patterns and future trends. residues. The location determines the collection costs. If these costs are higher than the economic value of the Calculate technical potential: A method for estimating residues, they will not be used for fuel. crop residues is to use the crop residue index. This is defined as the ratio of the dry weights of the residue Not all residues are available for energy production. produced to the total primary crop produced for a The use of agricultural residues for fuel must com- particular species or cultivar. pete with alternative uses, particularly with the need to preserve soil fertility, retain moisture, and provide Technical potential = yearly crop production x RPF. soil nutrients, as well as various other uses of which 64 Annex 5: Determination of Yield from Agricultural Crops and Residues fodder, fiber, and fuel are the most common. Thus, for households and rural industries. The method is simple environmental or financial reasons, part of the resi- and straightforward, but it has a number of flaws, dues is not available as biomass fuel. which may result in reliability issues and thus poor col- lected data. Users are unlikely to closely monitor their To take into account the collection costs and the daily use (volume and/or weight) of freely available alternative uses, a recoverability factor (RF) is often agricultural residues, let alone detect any usage pattern defined. and long-term trends. At best, they can guess their cur- rent use. They may find it difficult to correctly recall Implementation potential = Technical potential x RF any year-to-year straw usage fluctuations as a result of higher or lower availability. And they may also give The common method to assess RFs is by interview- socially desirable answers. It is clear that a proper bio- ing prospective users of agricultural residues, such as mass assessment cannot rely on just one interview. 65 Annex 6: Guidelines for Planning a Biomass Resource Survey The Biomass Assessment Handbook (Rosillo-Calle experience. It may even be possible (or necessary) to and others 2006) presents useful guidelines for plan- interpolate figures from other regions and countries. ning a biomass resource survey: Again, critical examination of the data is essential for adequate evaluation. Decide on the size of the survey and the degree of detail required: What is the reason for the assessment, what Convert existing data to standard units to allow easy are the objectives, and what kind of action should fol- comparison between localities whenever possible. low? Decisions made at this stage will determine the type of questions asked, the survey methods used, and Consider demand and supply analysis: If data on bio- the funds and other resources required. mass supply is initially too difficult to obtain, the use of demand analysis data may help to fill the informa- Determine what data already exist: A great deal of tion gaps. time and money can be saved if some of the informa- tion required already exists, or if it can be obtained Decide on the feasibility and scope of field surveys: from existing data. Useful sources could include Ideally, information should always be verified by spe- national, regional, and local databases, and statistics cific field research where feasible. Field surveys will produced by both government and nongovernmental provide the most accurate and up-to-date informa- organizations. Published tables, graphs, and conver- tion, but they are difficult and expensive. sion tables may provide estimates of stock and yield for forests and woodland. Aim to collect time-series data: Only data collected over a number of seasons, say five years, will show Existing information should be carefully examined trends in use and allow for climatic variation (both and interpreted by personnel with good judgment and annual and seasonal). 66 Annex 7: Finnish Research into Reducing Biomass Supply Costs The Finnish Wood Energy Technology Programme Otherwise, the truck is equipped with a trailer, and (1999­2003) aimed to drive down the cost of wood the load volume is typically 100­130 m3. fuel supply, placing strong emphasis on researching · Queuing of fuel trucks is an unnecessary cost factor the development and optimization of logistics. Some that should be eliminated. Queuing may occur at interesting findings from the program include the large plants, especially in cold winter weather when following: the need for fuel is high. The peak time of arriv- als is typically in the morning. To avoid queuing, · Moving comminution to an end-use facility or bottlenecks should be removed from the receiving terminal was found to be an effective measure for system, and the arrivals should be scheduled. enhancing the reliability of the procurement sys- · Unfortunately, little compatibility among machines tem. Residue bales help to smooth the logistics: has been achieved in the forest chips procurement the system becomes less vulnerable, waiting times chain. The lack of compatibility is because forestry between machines are eliminated, winter storage is conditions vary from the early uncommercial thin- facilitated, and the entire process becomes easier to ning of young stands to the final harvest of mature control. Residue baling technology is only suitable stands, and because the technology is still in its for large-scale operations, and the availability of a infancy. Several alternative production systems are crusher at the end-use facility is a precondition. The in use, each employing special equipment that is crusher makes it possible to receive stump and root not necessarily compatible with other systems. This wood as well, and the raw material base and fuel diversity causes problems in practice. Contractors' supply are consequently broadened. Large 150 m3 flexibility is restricted, and investments become risky truck-and-trailer vehicles have been built to trans- when technology prevents changing from one sys- port loose forestry residues, residue bales, unde- tem to another. Furthermore, machine markets are limbed tree sections, and stump and root wood to fragmented, manufacturing in series is not possible, the plant, separately or mixed. and machine prices remain high. Therefore, when- · It nevertheless remains more common that for- ever possible, it is preferable to use conventional est fuels arrive at the end-use facility as chips. If equipment for the harvesting and transportation the distance is short, the landing site crowded, or of forest biomass. This philosophy is also recom- reception at a plant limited, the truck does not use mended for China. However, special equipment a trailer. The maximum load volume is then 60 m3. remains a necessity in many phases of the chain. 67 Annex 8: Sample Biomass Fuel Supply Contract SPECIMEN BIOMASS SUPPLY CONTRACT FOR (SITE) Source: CarbonTrust(http://carbontrust.co.uk/technology/technologyaccelerator/biomass-online-resources.htm) Contract between and for the supply of solid biomass to . Preamble: a. is the private/public company, whose registered office is at
, Company Number XXXX, hereinafter referred to as "the supplier"; b. is the private/public company whose registered office is at
, Company Number XXXX, hereinafter referred to as "the end user"; c.
is the site (owned and) operated by the end user where the delivery of biomass is required by the end user, hereinafter referred to as "the site." 1. Contract 1.1. The supplier agrees to supply to the end user and the end user agrees to purchase from the supplier biomass to the specifications, in the quantities, for the period, at the price, and on the terms and conditions set out below. 1.2 For the purpose of maintaining control over the necessary quality, the end user agrees neither to purchase nor use biomass from any other source or supplier except where the supplier is unable to provide deliveries or meet biomass specification requirements within three working days of the due date. 2. Biomass specification 2.1 Moisture content. The target moisture content on a wet basis shall be XX% by weight based on the [rel- evant standards] [see guidance notes] but in any event shall not exceed XX%. 2.2 Contaminants such as soil or stones, metal and plastics should be less than 2% by weight of the total bio- mass load. 2.3 The biomass particle size shall comply with the [relevant standards]. 3. Duration of contract 3.1 This contract is for a period of and will commence on and end on , (with a formal review after the first three months of the contract to assess the need for any adjustments to the contract). Any adjustments need to be agreed jointly between the end user and supplier. If the supplier or end user cannot agree or meet adjustments, each party should be able to terminate after 3 months if it wishes to. 3.2 This contract may be extended by agreement of both parties not less than three months before the end of the original contract period. 68 Annex 8: Sample Biomass Fuel Supply Contract 3.3 In the event of either party failing to meet their contractual obligations under this agreement the other party has the right to terminate the contract at three months notice unless such breach of contract is rem- edied by the defaulting party to the reasonable satisfaction of the non-defaulting party. If any material breach is committed by either party which, in the reasonable opinion of the non-defaulting party, cannot be remedied within 10 working days the non-defaulting party may terminate this agreement immediately by way of written notice. 4. Quantity 4.1 The minimum monthly quantity of biomass supplied during the defined contract will be XX cubic metres OR XX tonnes (delete as appropriate) at the specification defined in Clause 3. 4.2 The end user may order amounts in addition to that specified in 4.1 by requesting an additional delivery from the supplier, specifying the quantity required, and the date and time by when the end user requires the delivery in accordance with Clause 7.4. If the supplier is able to satisfy the request, it shall notify the end user accordingly and deliver the amount requested as soon as is reasonably practicable. The supplier may charge the contract price for any additional delivery made in accordance with Clause 5. If the supplier cannot satisfy the request, it shall notify the end user of the reason why. 5. Price 5.1 The price for biomass delivered into the fuel store of the end user will be based upon the following tariff up until (delete as appropriate): · £XX per m3 of biomass; OR: · £XX per tonne of biomass. 5.2 Loads of different volumes/weights (delete as appropriate) will be charged on a pro rata basis in accor- dance with the above rate. 5.3 The price of the biomass will be upgraded annually [see guidance notes] and increased in of each year in agreement with the end user. 6. Fuel sources 6.1 The biomass will be derived from the following sources (delete as appropriate): · licensed harvested forestry timber; · sawmill residues; · arboricultural arisings; · short rotation coppice (SRC); ·agricultural arisings (e.g. straw); ·energy crops, such as miscanthus; ·clean recycled wood, exempt from the Waste Incineration Directive. The parent source of the biomass is declared as being (insert as appropriate). 7. Delivery of biomass 7.1 Biomass will be supplied in bagged/baled/loose form [delete as appropriate] and delivered to the end user by a suitable vehicle for delivery into the end user's fuel store. 7.2 A risk assessment and method statement shall be prepared in advance by the supplier following an initial site visit and discussion with the end user, to take account of the hazards on site and the risks posed to pedestrians, vehicles and property on the site during biomass delivery and offloading. This shall be for- mally reviewed annually, or whenever a change to the hazards and risks on site are identified. 69 Fuel Supply Handbook for Biomass-Fired Power Projects 7.3 On the dispatch of any consignment of biomass, the supplier shall send a Delivery Note and a Fuel Qual- ity Declaration to the end user by electronic mail or facsimile. A paper copy of the Delivery Note shall be provided to the end user at the site(s) with the delivery of each consignment. 7.4 The notice period for requesting delivery of biomass from the end user will be a minimum of XX days. 7.5 Responsibility for checking levels of biomass within the fuel store and informing the supplier of the need for a fuel delivery rests with the end user. 7.6 In the event of the requirement for a delivery at less than the notice period in clause 7.4 an additional fee of £XX will be payable to cover the costs of an emergency delivery. 7.7 Unless otherwise agreed in advance with the end user, deliveries shall be made between the hours of XX.00 and YY.00, or any other time agreed with the end user in advance between Monday and XXXday. 7.8 If a delivery cannot be made within the hours specified in the contract and the whole or part of the deliv- ery is not possible due to obstructions on the end user's site that are beyond the control of the supplier, the supplier will be entitled to compensation to cover the cost of transport and payment of an additional surcharge of XX% of the value of the biomass ordered, unless the end user informs the supplier of said obstruction within the notice period specified in Clause 7.4 above. 7.9 Upon delivery of the biomass to the end user, visual checks shall be made by the end user to ensure confor- mity to the agreed specification. 7.10 If checks reveal that the biomass does not conform to the agreed specification as per Clause 2, the end user reserves the right to reject the load in full. In the event that it is not possible to visually check the fuel load until it is in the fuel silo, but the woodchip is subsequently found to not conform to the agreed specifica- tion within 24 hours of delivery, then the end user reserves the right to reject the fuel. Rejected fuel will be removed by, and at the expense of, the supplier. Any such dispute over the specification of the biomass will be resolved as per Clause 11. 7.11 The supplier shall be responsible for immediately clearing up any biomass spilt during offloading and shall provide suitable tools for this job. 7.12 The biomass shall remain at the risk of the supplier until delivery to the company is complete (that is, the biomass is offloaded into the end user's store), when ownership of the biomass shall pass to the end user. 8. Sampling 8.1 The end user may at any time send representative samples of biomass for evaluation, analysis, testing and approval. All samples must meet the specification. Such tests are to be at the end user's expense. 8.2 The strategy for maintaining the original quality of the biomass once the supplier has delivered it on site is the responsibility of the end user. 9. Terms of payment 9.1 The supplier will invoice the end user on a monthly basis. This will be based upon the number of loads recorded (by weight or volume) and will be assessed on the XX day of each month. The invoice amount will be the number of loads multiplied by the price per load adjusted for volume or weight as outlined in clause 5.1 plus the VAT rate in force at time of billing. 9.2 Terms are monthly payment at XX days from date of invoice. 9.3 In the event that any payments are overdue the supplier has the right to refuse to make further supplies until all outstanding overdue invoices have been settled. 9.4 Interest shall be payable on amounts overdue at the daily published Bank of England base rate plus 2%. 70 Annex 8: Sample Biomass Fuel Supply Contract 10. Other terms and conditions 10.1 Boiler outage or operational problems that are a direct result of sub-standard maintenance, boiler misuse/ neglect or boiler defects are not the responsibility of the supplier. In this instance, any cost that is incurred by the supplier as a result of not being able to deliver fuel will be charged to the end user. 10.2 The supplier will indemnify the end user against the cost of repair to fuel handling and combustion equip- ment caused by the supplier or supply of biomass not in accordance with the specification set out in clause 2.1, 2.2 and 2.3, with the exception of consequential losses such as having to pay for heat supplied from other sources to a limit of £XXXX [see guidance notes]. 10.3 The supplier will have public liability insurance of £5,000,000/10,000,000 [see guidance notes]. 10.4 The supplier's liability under this Agreement (including under any indemnity) shall be limited to £XXXX [see guidance notes]. 11. In the event of a dispute 11.1 Both parties shall attempt in good faith to negotiate a settlement to any dispute between them arising out of or in connection with the contract within thirty days of either party notifying the other of the dispute. Initially the party who wishes to bring the dispute to the notice of the other will do so in writing. The other party will respond to this in writing within 5 working days of receiving the notification of a potential dispute. Where the potential dispute relates to on-site issues at either the end-user or supplier sites, a joint site meeting will normally take place within 8 working days of the potential dispute being brought to the other party's attention. 11.2 Where a resolution has been agreed after one or more meetings, including a site meeting (if appropriate), this shall be communicated in writing and noted by both parties. 11.3 Where a resolution cannot be agreed after several attempts, the parties will attempt to settle it by media- tion in accordance with the Centre for Effective Dispute Resolution (CEDR) Model Mediation Procedure. Unless otherwise agreed between the parties, the mediator will be nominated by CEDR. 12. Force Majeure 12.1 A party, provided that it has complied with the provisions of clause 12.3, shall not be in breach of this agreement, nor liable for any failure or delay in performance of any obligations under this agreement (and, subject to clause 12.4, the time for performance of the obligations shall be extended accordingly) arising from or attributable to acts, events, omissions or accidents beyond its reasonable control (Force Majeure Event), including but not limited to any of the following: (a) Acts of God, including but not limited to fire, flood, earthquake, windstorm or other natural disaster; (b) war, threat of or preparation for war, armed conflict, imposition of sanctions, embargo, breaking off of diplomatic relations or similar actions; (e) compliance with any law; (f) fire, explosion or accidental damage; (h) extreme adverse weather conditions; (i) collapse of building structures, failure of plant machinery, machinery, computers or vehicles; (j) any labour dispute, including but not limited to strikes, industrial action or lockouts; (k) non-performance by suppliers or subcontractors (other than by companies in the same group as the party seeking to rely on this clause); and (l) interruption or failure of utility service, including but not limited to electric power, gas or water. 71 Fuel Supply Handbook for Biomass-Fired Power Projects 12.2 The corresponding obligations of the other party will be suspended to the same extent as those of the party first affected by the Force Majeure Event. 12.3 Any party that is subject to a Force Majeure Event shall not be in breach of this agreement provided that: (a) it promptly notifies the other parties in writing of the nature and extent of the Force Majeure Event causing its failure or delay in performance; and (b) it could not have avoided the effect of the Force Majeure Event by taking precautions which, having regard to all the matters known to it before the Force Majeure Event, it ought reasonably to have taken, but did not; and (c) it has used all reasonable endeavours to mitigate the effect of the Force Majeure Event to carry out its obligations under this agreement in any way that is reasonably practicable and to resume the performance of its obligations as soon as reasonably possible. 12.4 If the Force Majeure Event prevails for a continuous period of more than six months, any party may termi- nate this agreement by giving 14 days' written notice to all the other parties. On the expiry of this notice period, this agreement will terminate. Such termination shall be without prejudice to the rights of the par- ties in respect of any breach of this agreement occurring prior to such termination. 13. Third party rights A person who is not a party to this agreement shall not have any rights under or in connection with it. 14. Governing law and jurisdiction 14.1 This agreement and any dispute or claim arising out of or in connection with it or its subject matter shall be governed by and construed in accordance with the law of England and Wales. 14.2 The parties irrevocably agree that the courts of England and Wales shall have exclusive jurisdiction to settle any dispute or claim that arises out of or in connection with this agreement or its subject matter. Agreed this Name ______________________________ Position ______________________________ (On behalf of ) Name ______________________________ Position ______________________________ (On behalf of ) 72 Annex 8: Sample Biomass Fuel Supply Contract GUIDANCE NOTES FOR COMPLETION OF BIOMASS FUEL SUPPLY CONTRACT (WEIGHT OR VOLUME) These guidance notes are intended to assist with the completion of the specimen supply contract for biomass by weight or volume. Neither the specimen contract nor the notes are intended to be prescriptive, and consideration must be given to site specific issues and the supplier/end user relationship. Both parties are advised to seek legal advice before entering into a legally binding contract. For additional background information on biomass fuels, storage, handling and a range of other relevant information the Carbon Trust's guide to biomass heating is avail- able for download via the website: www.carbontrust.co.uk/biomass. Preamble. This section is normally straightforward. However, the end users may not necessarily own the site or the instal- lation--they may be operating it on behalf of a client (the owner), in which case the owner of the site needs defining separately in this part of the contract. 1. Contract The supplier and end user may mutually agree that clause 1.2 is overly restrictive--it may be necessary in terms of quality control, yet restricts the end user from sourcing alternatives should there be any doubt about the security of supply from a single supplier. Alternatively, the end user may choose a biomass co-operative (such as South West Wood Fuels) in which case, whilst only one supplier provides biomass to the end user, it will have been sourced from multiple suppliers earlier in the supply chain. 2. Biomass specification The appropriate biomass specification will depend on the fuel type (see Section 6), and to some extent on the performance specification of the boiler. Standards are vital for biomass to become a commodity fuel which end users can buy with confidence. The European Committee for Standardization (CEN) formed a technical committee (CEN/TC 335­Solid Bio- mass) to develop standards to describe all forms of solid biomass within Europe, including wood chips, wood pellets and briquettes, logs, sawdust and straw bales. The standards allow all relevant properties of the fuel to be described, as well as the physical and chemical characteristics of the fuel, methodologies for sampling and assessment of moisture content, etc. Whilst some of these standards are still in draft form, they are becoming more widely used in the UK, and are readily available from several sources, including the Biomass Energy Centre (www.biomassenergycentre.org.uk). Alternatively, the Austrian Standards Institute (Österreichisches Normungsinstitut, referred to as ONORM) Standard M7 133 or the German Institute for Standardization (Deutsches Institut für Normung) DIN 66 165 tend to be de facto across Europe and are widely used in the UK. Ultimately, the end user should seek advice from the boiler manufacturer so as not to compromise any warran- ties, then select the most appropriate biomass specification in line with the manufacturer's recommendations. 3. Duration of contract The supplier and end user may agree an appropriate supply contract period of between 1 and 5 years. It is sug- gested that a sensible period of notice for either contract extension or termination would be three months, but this can be varied by agreement between the supplier and end user as required. 73 Fuel Supply Handbook for Biomass-Fired Power Projects 4. Quantity This contract template allows for supply by either volume or weight subject to the end user and supplier agreeing their preferences. Whilst the energy content of wood by weight varies very little between different timber species, the density varies significantly. Therefore, if the end user is purchasing biomass by weight, the species of timber should not mat- ter (although clearly the moisture content of the biomass will). However, if purchasing biomass by volume, the energy content will be dependent upon the timber species; for example, the typical calorific value of softwood chips at 30% moisture content is 0.70 MWh/m3, compared to 1.02 MWh/m3 for hardwood chip at 30% MC. In addition, the bulk density will vary considerably, resulting in a highly variable volume expansion from 1 m3 of solid wood to anywhere between 2 and 5.5 times the original volume when chipped. Foresters tend to work in volume. Arguably though, purchase by weight is less problematic provided that the moisture content is specified and agreed in advance (based on the boiler specification), and that the supply com- plies with that agreed moisture content. It is important from the supplier's perspective that a prescribed quantity (by weight or volume) is agreed contrac- tually, whilst making provision for the end user to request additional biomass as required (but with reasonable notice). 5. Price It is generally accepted that fresh felled wood of most species weighs about 1 tonne per solid cubic metre, but as the wood becomes air dry it loses between one quarter and one half of its weight. Appendix 1 illustrates how this varies between species. However, the volume increases when wood is chipped. As a general rule of thumb, 1 tonne of woodchip will be equivalent to 4 cubic metres of chip. However, this conversion must be used with caution, as it does not take account of varying moisture content. The final price (for either weight or volume) will depend on numerous factors, including the biomass quality, local market conditions, availability, and distance of travel. End users are recommended to appraise the local market to determine benchmark prices before negotiating the final price with the selected supplier. The price should then be indexed by setting an initial price based upon the full costs of supplying the biomass to the site. The initial price then changes over time by periodically applying agreed indexation. However, the issue of an appropriate index for biomass is a complex one. Whilst it is important that biomass costs continue to be competitive vis-à-vis fossil fuel prices in order to maintain economic viability for the end user, biomass suppliers also need to be able to make a profit margin sufficient to maintain the economic viability of their business. The rising cost of fossil fuels will invariably have a knock-on effect to the price of biomass (i.e. with respect to har- vesting, processing and transportation costs, all of which are processes reliant upon fossil fuels). There are a number of different forms of indexation which could be applied: · A price index for a major fuel such as the index for a heavy fuel oil (or gas) for [medium] sized manufacturing companies produced by the Department for Business, Enterprise and Regulatory Reform as contained in the Quarterly Energy Prices (e.g. Table 3.1.1: Percentage price movements between Q2 2007 and Q2 2008 for heavy fuel oil (HFO), electricity and gas, by size of consumer, for manufacturing industry) which can be found at http://www.berr.gov.uk/files/file47741.pdf; 74 Annex 8: Sample Biomass Fuel Supply Contract · A general index as an agreed proportion of the Retail Price Index (RPI), except that if haulage costs (a critical cost factor for biomass fuel) increase by more than twice RPI in one 12 month period, the fuel supplier has the right to re-open discussions on prices; · The price could simply increase at an agreed rate per annum e.g. 2% or 5%. The most appropriate indexation should ultimately be mutually agreed between the supplier and the end user. 6. Fuel sources The source of biomass will depend to some extent upon availability in the local area. The contract is designed to be able to support the supply of a wide range of biomass fuels, including straw, cord wood, wood chip, wood pellet, short rotation coppice (SRC) such as poplar and willow, grass and non-woody energy crops such as Mis- canthus (Miscanthus giganteus), Switchgrass (Panicum virgatum), Reed canary grass (Phalaris arundinacea), Rye (Secale cereale), Giant reed (Arundo donax), and Hemp (Cannabis sativa). 7. Delivery of biomass Conditions for delivery of fuel will be site dependent, but need to fully take account of the health and safety risks to pedestrians, vehicles and property on the end user site. It is important that the supplier conducts a site survey well in advance, and identifies all risks and hazards on site before negotiating with the end user the most appropriate days and times of delivery. For example, if the installation is at a school, it may be considered more appropriate that delivery times to site are outside of normal school hours, in order to minimise the risk to pupils. Equally, the attendance during deliveries of an end user representative (e.g. Maintenance Operative, Site Supervi- sor) may be necessary for both health & safety and security reasons. Weekend deliveries may be acceptable or preferable at certain sites, depending on security policies and access arrangements. 7.4 In terms of notice periods for deliveries, the supplier may need 3­7 days in order to plan the delivery. 7.5 If the end user is remote and has no one on site, responsibility for determining fuel levels may be assigned by prior agreement to the supplier. 8. Sampling Current relevant standards for sampling include CEN Appendix 1: Technical Specification 14778-1, Solid Biomass­ Relation between weight and volume Sampling­Part 1: Methods for Sampling and/or CEN of air dried wood Technical Specification 14778-2, Solid Biomass­Sam- pling­Part 2: Methods for sampling particulate mate- Air dried wood Weight kg/m3 rial transported in lorries. Both specifications may be considered unnecessarily complex for certain sites, Beech, oak 750 however. Part 2 is most relevant to a large capacity Ash, birch 716 plant receiving multiple lorry deliveries per day. Sycamore 662 Elm 581 Where moisture content is the critical factor, CEN Poplar 486 Technical Specification 14774-2:2004 Solid bio- Pines 550 mass--Methods for the determination of moisture content--Oven dry method--Part 2: Total moisture-- Spruces 465 Simplified method may be considered the most appro- Larch 560 priate methodology. Douglas fir 580 75 Fuel Supply Handbook for Biomass-Fired Power Projects 9. Terms of payment This must be agreed in advance to avoid any dispute The date of invoicing may depend upon the end user's at a later date. financial accounting periods, whilst payment terms will depend upon the supplier's standard terms and It is important that the limit on liability at Clause 10.2 conditions of sale. Both must be agreed in advance to and 10.4 is agreed at an appropriate figure. This should avoid any dispute at a later date. be representative of the end user's possible total loss but market practice is typically that such a sum does 10. Other terms and conditions not exceed the maximum value of the contract to the The level of the supplier's public liability insurance supplier (that is, the value of the total volume of fuel may depend on the end user's standard requirements. to be supplied over the course of the contract). 76 Annex 9: Energy Density of Forest Chips Heating value is determined per unit mass of dry or Therefore, the differences are larger when calculations fresh fuel. Since woody biomass is frequently bought are made on a volume basis. Energy density is highest and measured by volume, and transport and storage in chips from high-density species, such as oaks. In the facilities are built by volume rather than mass, it is Nordic forests, a solid cubic meter of birch bark has also important to know the effective heating value per a heating value equal to 0.30 tons of oil equivalent unit volume. This is the energy density of a fuel. The (toe). The corresponding figure for Scots pine bark is basic density, that is, the oven dry mass per green vol- only 0.13 toe (see table A9.1). ume in kg/m3, serves as a conversion factor from mass to solid volume. In forestry the primary unit of volume is cubic meters (m3) solid wood. For biomass chips, although m3 Variation in the basic density of tree species and bio- solid is a practical unit for comparison between tim- mass components is considerably greater than the ber varieties with varying bulk density, m3 loose is a variation in the effective heating value of dry mass. more commonly used (although less accurate) unit. Table A9.1 The Energy Density of Forest Biomass Chips and Crushed Bark in Finland at 40 Percent Moisture Content Energy density Source Basic density, kg/m3 MJ/m3 kWh/m3 toe/m3 Whole tree Scots pine 395 7,100 1,970 0.169 Norway spruce 400 7,020 1,950 0.167 Birch 475 8,270 2,300 0.197 Bark Scots pine 280 5,460 1,520 0.130 Norway spruce 360 7,090 1,970 0.169 Birch 550 12,490 3,470 0.297 Crown without foliage Scots pine 405 7,780 2,160 0.185 Norway spruce 465 8,400 2,330 0.200 Birch 500 9,040 2,510 0.215 Crown with foliage Scots pine 405 7,660 2,130 0.183 Norway spruce 425 7,730 2,150 0.184 Source: Richardson and others 2002. 77 Fuel Supply Handbook for Biomass-Fired Power Projects Therefore, the bulk density or solid content of chips, · Season: Frozen biomass produces finer material that is, the ratio of solid volume to loose volume of during comminution because of brittleness. This chips, must also be known. The solid content of chips results in a higher solid content. is affected by the following factors: · Loading method: Blowing chips through the dis- charge spout of a chipper into a truck increases the · Particle shape: The greater the diagonal-to-thick- solid content per unit volume to a greater extent ness ratio in chip particles, the lower the solid than freefall from a conveyor, tractor bin, loader, content. or silo. Blowing from above gives a higher solid · Particle size distribution: Material with a heteroge- content than lateral blowing. The stronger the neous size distribution has smaller spaces between fan pressure, the greater the compaction of the particles. Chipped fuel from whole trees or forestry particles. residue contains more fine material than uniform · Settling: The solid content of a chip load increases chips from pulpwood logs and tends to have a during transport because of vibration and settling. higher solid content. Factors contributing to settling are the initial solid · Tree species: Fuel chips from brittle, low-density content of the load, length of haul, evenness of the material contain more fine particles and have a road, and possible freezing of the chips. Settling higher solid content. takes place rapidly at first, but slows down after · Branch content: Fresh branches and pliable twigs the first 10­20 km of travel. From the standpoint tend to produce long particles that reduce the solid of transport efficiency, the solid content before content of chips. haulage is more important than the content after · Storage: Stored biomass tends to contain more fine haulage. material and fewer long particles than fresh mate- rial. The solid content is slightly higher than that of The solid content of fuel chips varies between 38 per- chips from fresh biomass. cent and 44 percent, depending on the factors listed Figure A9.1 Examples of the Energy Density of Selected Fuels, Showing the Load Volume Required for 1 toe 18 16 14 load volume required (m3) 12 10 8 6 4 2 0 fuel oil coal wood pellets sod peat wood chips, milled peat wood chips, wood chips, HDW MDW LDW fuel type Sources: BTG; Drohm Design & Marketing based on Richardson and others 2002. Note: HDW, MDW, LDW refer to high-, medium-, and low-density wood. 78 Annex 9: Energy Density of Forest Chips above. A commonly used conversion factor is 40 As industrial demand for biomass chips increases, the percent. A solid cubic meter of wood thus produces average distance between utilization point and source approximately 2.5 m3 loose of chips. Low energy den- will increase, as will the cost of transportation. In con- sity is a problem associated with biomass chips. The trast to fossil fuels, economy of scale becomes negative space required for transporting and storing a given for wood-based fuels, although bulk transportation quantity of energy in biomass chips is 11­15 times (train or ship) can make the operation less dependent greater than that needed for oil and 3­4 times that on distance. To control the cost of fuel in large instal- required for coal, resulting in higher costs. For this lations, forest biomass chips are often cofired with reason, fuelwood is traditionally and ideally used bark, sawdust, peat, coal, or municipal waste. close to the source. If woody biomass is ground, dried, and pressed into pellets, its energy density is increased significantly (see figure A9.1). 79 Annex 10: Alternatives for Reflecting Energy Content in Biofuel Price This annex is based on van Loo and Koppejan (2008). the bulk densities of all delivered biomass fuels to be determined prior to the first delivery, to improve the Recommended method: The recommended method of accuracy of the assessment process. The uncertainty of reflecting energy content in the price of the biofuel is this method is that (a) the estimation or measurement to calculate its energy content based on weight and net of the volume delivered is in most cases less precise calorific value (NCV). A typical method is to weigh than a weight measurement, and (b) the bulk density the load at a scale house and to measure the mois- of biomass fuels varies. ture content of samples from the load using a mois- ture meter that provides quick results. The NCV can Alternative 2: Another alternative is to calculate the fuel be calculated using the gross calorific value (GCV) of price based on the amount of heat produced from the the delivered fuel and the moisture content obtained plant according to heat meter measurements. The effi- from the measurements (see section 2.2). The GCV ciency of the combustion plant should be taken into of each fuel source should be determined by chemical account, so that reasonable market prices for the fuel analysis prior to the first delivery. The energy content are achieved. An advantage is that there are no costs for is calculated by multiplying the NCV by the weight of mass, volume, or moisture content determinations, and the biomass fuel, which then factors into the price of calibrated heat meters are very accurate. A disadvan- the delivered fuel. tage is that it is quite difficult to allocate the produced heat to a specific fuel amount from a specific supplier if Alternative 1: An alternative, but less accurate, assess- there are multiple fuel suppliers. Another disadvantage ment method, which can be used when no scale house is the influence of operating conditions on plant effi- is available, is based on a measurement of the delivered ciency, because this would reduce the fuel price (insuf- volume rather than weight. The volume can be con- ficient boiler cleaning can decrease boiler efficiency). verted to weight by using the average value of the bulk Finally, during storage, the energy content of the fuel density of the specific biomass fuel. It is important for can decrease, which would also reduce the fuel price. 80 Annex 11: Example of the Sampling and Handling Process for Wood Fuels Simple samples (increments) of at least 1 liter Combined samples · necessary number of samples · at 5 liters Duplicate laboratory samples Mixing and division Laboratory sample Crushing <25 mm (when needed) 2 samples of 0.3­1.0 liters Mixing and division Moisture samples Method 2 (about 0.5 literb) Method 1 (about 0.5 litera) Air Calorific value sample drying Reserve sample Mixing and division at least 2 liters · <0.5 mm Grinding · at least 5 liters Mixing and division Analysis samples · at least 0.5 liter · necessary number of duplicate samples Sources: BTG; Drohm Design & Marketing based on Impola 1998. Note: a. In proportion to mass of dry matter. b. In proportion to quantity of wood fuel. 81 Annex 12: Quality Management System for Solid Biomass Supply Langheinrich and Kaltschmitt (2006) developed a to use a flow diagram to describe all unit opera- six-step methodology for designing a quality man- tions and their links. chapters 4 and 5 of this hand- agement (QM) system for solid biomass supply. They book describe the supply chain for agricultural recommend that the practical implementation of the and forestry residues, respectively. Describing QM system be set out in an operator manual. The the supply chain in this manner helps to struc- six steps, fine-tuned where relevant to the supply ture the unit operations logically, determine links, of agricultural and forestry residues, are described and identify process owners for the allocation of briefly below. responsibilities. 1. Description of Process Chain 2. Determination of Customer Requirements The operator manual starts with a complete descrip- Next, the customer requirements are determined tion, with a sufficient level of detail, of all individual (figure A12.1). These requirements depend on steps (unit operations) of the supply chain, from col- previous and subsequent unit operations. The lection of agricultural and forestry residues to deliv- product requirements at the unit operation level ery at the biomass power plant. It is recommended may be different from a product standard that Figure A12.1 Determination of Customer Requirements Requirements to be demanded Requirements to be demanded of a previous process of a subsequent process Previous Unit operation Subsequent process under consideration process Customer requirements from Customer requirements from a previous process a subsequent process Sources: BTG; Drohm Design & Marketing based on Langheinrich and Kaltschmitt 2006. 82 Annex 12: Quality Management System for Solid Biomass Supply would be applicable to the final product. However, · The point at which raw materials are collected or the requirements of the next operator in the supply purchased; chain should always be met. Each operator should do · The point at which raw materials are preprocessed the following: and loaded for delivery to the next point in the chain and within the premises of the final supplier; · Ascertain that the feedstock from the previous pro- · The points at which the condition of the material is cess is in compliance with the relevant CEN/TS (or can be) changed deliberately; 1496117 standard. · The point at which the final product is loaded for · Take into account the likely variability of relevant delivery; and properties of the feedstock and other factors. · The point of delivery at the end users' premises. · Take into consideration documentation and logisti- cal demands, since logistics are of great importance 5. Selection of Appropriate Quality among qualitative properties. Assurance Measures Depending on the results from previous steps of the 3. Analysis of Quality-Influencing Factors methodology, appropriate quality assurance mea- Step 3 involves an analysis of the factors that have the sures have to be identified and applied. The following most influence on biomass fuel quality. Typical factors aspects should be taken into account: include the following: · Allocation of responsibilities, · Effectiveness of preliminary inspections of fuel · Elaboration of work instructions, sources; · Proper documentation of processes and test · Effectiveness of checking incoming loads; results, · Appropriateness of applied methods to handle, · Training of staff, store, and process materials; · System for complaint procedures, · Quality control measures adopted; · Customer satisfaction and maintenance of the qual- · Company management and responsibility; and ity assurance system, · Qualification and knowledge of staff. · Preliminary inspection of raw material suppliers and formulation of acceptance criteria, 4. Identification of Critical Control Points · Enforcement of quality assurance meetings, and Critical control points, that is, the interfaces between · Failure mode and effect analysis. processes, should be identified with a view to minimiz- ing the costs of quality control and to laying the foun- 6. Routines for Nonconforming Materials dations for a traceability system. Data on the origin of When visual inspection or test methods show that the the feedstock and on the processes that the feedstock raw material at the gate of the plant does not con- has undergone are systematically collected and ana- form, the load should be rejected (before tipping of lyzed. Critical control points include places at which the load). Appropriate procedures must be in place for relevant properties can be most readily assessed and dealing with varying degrees of nonconformity. When places with the largest potential for quality improve- nonconformity is discovered, a nonconformity report ment and/or cost-reduction interventions: must be generated, and handling agreed on with the end user. 17. The European Technical Standards for solid biomass fuels. 83 Annex 13: Fuel Supply Risk Matrix Potential consequences Cause (fuel supply risk examples) (event) Probability Impact Mitigating factors · Low availability of biomass Price of biomass High High · Determine benchmark prices · Competing usage fuel (raw material) · Commission independent market · Fuel supplier controlling fuel supply increases; future study · Old fuel sources dry up escalation · Enter into long-term fuel supply contracts · Contract with multiple fuel suppliers · Allow fuel flexibility and ensure availa- bility of back-up fuel · Lower harvest capacity as a result Procurement costs High High · Commission biomass resource assess- of bad harvest conditions or limited of biomass fuel ment to ensure required land is availa- terrain accessibility increases (logistics ble within reasonable transportation · No mechanized methods for of supply) distance biomass collection, storage, and · Enter into long-term fuel supply transport contracts · Transportation distance increases · Control transportation · Higher machinery expenses because · Require densification of biomass to of breakdown or other unexpected reduce transport costs situations resulting in lower net · Make the fuel supplier financially output involved in plant operation · Lack of practical experience · Arrange planting schemes with growers or forest owners · Develop storage capacity for conti- nuous operation · Contract for fixed time schemes for biomass fuel delivery · Train staff; provide clear work instruc- tions; allocate responsibilities (continued) 84 Annex 13: Fuel Supply Risk Matrix Potential consequences Cause (fuel supply risk examples) (event) Probability Impact Mitigating factors · Insufficient match between Insufficient agri- Moderate High · Enter into supply contracts that biomass fuel and fuel feed system cultural or forestry include standards and specifications (off spec) residues at the right · Monitor fuel quality (QM system) · Lack of practical experience specification to · Prove plant operation with variety of operate plant fuel specifications · Enter into contracts stating that biomass fuel not in compliance with specifications may be rejected or reduced in price (incentives or penal- ties to fuel suppliers and growers) · Train staff; provide clear work instructions; allocate responsibilities · Increase of transport costs Higher prices for Moderate Moderate · Enter into long-term contracts for · Higher ash content than foreseen ash removal ash removal · Change in legislation · Enter into contracts that include standards for ash quantity and quality · Absence of equipment to remove Presence of foreign Moderate Moderate · Use front-end screening to remove foreign objects objects interrupts foreign objects · Problems with fuel feed system operation · Ensure feeder redundancy and easy maintenance access to dislodge · Change in legislation Supplies halt Low High Obtain permits that allow as much because of the fuel flexibility as possible absence of required permits Source: Based on Thornley (not dated publication, and oral communication). 85 The Energy Sector Management Assistance Program (ESMAP) is a global knowledge and technical assis- tance trust fund program administered by the World Bank and assists low- and middle-income countries to increase know-how and institutional capability to achieve environmentally sustainable energy solutions for poverty reduction and economic growth.