Agricultural Pollution Plastics Why Care about the Use of Plastics in Figure 1: Plastic Debris in the Pacific Agriculture? Although the agricultural sector is not the largest user of plastics,1 their rapid appearance on farms the world over is quietly turning into a substantial pollution con- cern. Versatile and economical as they are, plastics are found all over farms. From machines to mulches, they are the stuff of bags and tubs, of tubes and tools, of tags and trays, and of pots and twine. Plastic films are used to cover greenhouses and hug plants around the root zone (see figure 9). Other kinds of plastics are used as ingredients in chemicals. Farms use millions of tons of Source: © The Ocean Cleanup. plastics each year, costing them billions of dollars, a tes- tament to how useful they are. To the extent that they est concern in parts of the ocean where these wastes are can help to save water, dissuade pests, suppress weeds concentrating (up to 580,000 pieces per km2). Yet deadly with less reliance on chemicals or fire, and save fuel plastic masses such as the Great Pacific Garbage Patch by lightening equipment and containers, some of their (see figures 1 and 6)—a vortex of floating plastic waste wide-ranging benefits include ecological ones. Yet more that is twice the size of France and killing wildlife on than unsightly, discarded plastics can damage farmland its way2—represent mere islands in the sea of plastic and cause harm to humans and wildlife alike, making waste that has already accumulated in the ocean.3 Most their celebrated durability a long-term pollution and agricultural plastics do not biodegrade (within a human public health worry. lifetime), but plastics do break down in many environ- Given the ubiquity of plastics in agriculture and ments, leading some to be ingested by humans and beyond, it is perhaps encouraging that plastics range wildlife depending on how they are disposed of. in toxicity, and that their drawbacks have much to do While it can be plain to recognize (as in the cases de- with how these are formulated, designed, used, and dis- scribed above and others, figures 1 and 7), plastic pollu- carded. Collecting, landfilling, recycling, and deriving tion is difficult to define and even harder to estimate. It energy from agricultural plastics offer potential for mit- can take decades or even centuries for plastics to fully igating some of the worst effects of discarded plastics. degrade, and some plastics do not degrade at all when Yet these are far from panaceas, and both materials and shielded from ultraviolet radiation or the right kinds of process innovation are needed to slow the progression bacteria (for example, in certain landfills). This raises the of the pollution problems to which agricultural plastics question of whether the very act of producing plastics is are contributing. a form of pollution, regardless of their final destination, or whether plastics only become polluting in certain en- Nature and Magnitude of the Problem vironments or forms. The latter might include when they Most agricultural plastics are single-season use and enter bodies of water, break down and are ingested, or are sooner or later, nearly all plastics end up in landfills, in- burnt and their uncontrolled emissions inhaled. Limited cinerators, waste-to-energy plants, or places where they data on the production, use, and disposal of agricultural were never intended to go—or remain. Used plastics plastics are available in the public domain, meanwhile, can be too costly to remove from farms, and hence are making it difficult to draw boundaries on the nature or left to pollute the land. Plastics are also pouring into the magnitude of this global pollution problem. world’s oceans. In 2010 alone, 4-12 million tons of plastic Data on the broader plastics market help to put fig- were estimated to wash offshore overall, causing great- ures on agricultural plastics in perspective, but also 1 Agricultural uses accounted for around 3.4 percent of the plastic use in the European Union (EU) in 2014. 2 Countless seabirds, turtles, and marine mammals die from getting entangled in plastic each year. 3 At least 250,000 tons (Eriksen et al. 2014). At the current, estimated rate of plastic refusal (from all sources), oceans will carry about 1 kg of plastic for every 3 kg of fish by 2025, and more plastics than fish by weight by 2050 (World Economic Forum 2016). This note was written by Emilie Cassou. Full references and acknowledgments are available online. Agricultural Pollution Plastics project a trend of rapidly rising use (especially in emerg- Figure 2: Plastic Films Headed for Burning in the Republic of Korea ing economies). Global plastics production has risen exponentially since the 1950s, rising twentyfold in 50 years from 15 million tons in 1964 to over 311 million tons of plastics in 2014.4 China was the leading producer that year (at around 26 percent), followed by the EU and the United States (around 20 percent each), and quickly gaining ground. Turning to the sparse figures available on agricultural plastics specifically, in the EU, demand for agricultural plastics was estimated at around 3.4 percent of overall plas- tics demand, or 1.6 million tons of agricultural plastics in 2015,5 not including plastics used in packaging or vehicles (which are tallied separately). At that level, if EU demand for agricultural plastics hypothetically accounted for 15–20 percent of the global demand, this would place the global demand for agricultural plastics around 8–10 million tons. Separately, the global agricultural market for plastic films alone was valued at US$5.87 billion as of 2012, correspond- Source: © Joshua Kraemer. ing to over 4 million tons sold, and was expected to nearly Note: Agricultural plastics commonly used to form greenhouses in the Republic of Korea are burned by farmers once worn out, contributing to dioxin contamination. double by the end of the decade by an industry analyst’s estimate (2013). China now has the largest agricultural area under plastic films in the world because of its rapid notably enabled that expansion to occur in cold and dry expansion into fruit and vegetable production—a response climates. The area under plastic cover in China grew more to dietary diversification there and abroad. Plastics have than 150-fold between 1982 and 2014, when it reached over Box 1: What Are Plastics? Figure 3: European Plastics Demand by Polymer Type, 2014 Plastics encompass a wide began in earnest. range of synthetic and naturally Plastics are broadly occurring substances that are appreciated for being low-cost, capable of flow, at which point lightweight, strong, durable, they can be molded, extruded, resistant to corrosion, and cast, spun, or applied as coating. nonconductors of electricity. Yet Synthetic plastics, also known plastics are extremely diverse as plastic resins, refer to several and versatile (figure 3). There dozen families of organic high are several dozen families of polymers, which are large, resins, each of which counts a chainlike molecules that contain vast array of grades, varieties, carbon. Polymers are formed by and characteristics. Two broad causing short-chain hydrocarbon categories of plastics that are molecules, or monomers, to commonly recognized are bond though a process known thermosets, which cannot as polymerization. These return to their original form monomers are typically oil- or once cooled and hardened, gas-derived, though bioplastics and thermoplastics, which are derived from alternatives to soften when heated and can Source: © PlasticsEurope, Consultic, myCeppi. fossil fuels such as vegetable be reshaped to form fibers, Note: EU-28 + Norway and Switzerland. fats and oils, plant starch, and packaging material, and microbiota. The first synthetic films. Both are found across a polymer was derived at the turn multiplicity of applications on high density polyethylene (HDPE) film), low density polyethylene of the 20th century, and during farms. Widely used resins in used for chemical containers, (LDPE), which is clear and the 1940s and 1950s, the mass packaging and films include vinyl (polyvinyl chloride [PVC] flexible, polypropylene (PP), and production of synthetic plastics polyethylene terephthalate (PET), used to make breathable polystyrene (PS). 4 Not all resins are counted in this tally by PlasticsEurope. Includes plastic materials (thermoplastics and polyurethanes) and other plastics (thermosets, adhesives, coatings, and sealants). Does not include the following fibers: PET, Polyamide (PA), PP, and polyacryl fibers. 5 Of 46.3 million tons overall, counting plastic materials (thermoplastics and polyurethanes) and other plastics (thermosets, adhesives, coatings, and sealants), but excluding PET, PA, PP, and polyacryl fibers. Source: PlasticsEurope. Agricultural Pollution Plastics Figure 4: The Spread of Plastic Mulch in China, 1991, 2001, 2011 Source: China Rural Statistical Yearbook for 1992, 2002, 2012. Note: Red, orange, and yellow shading indicate the most intensive use of agricultural plastics in kilograms per hectare. 18 million hectares, or roughly half the area of the Nether- plastic substances are endocrine-disrupting, and some lands (see increasing intensity in figure 4). are carcinogenic and harmful to the nervous and immune Looking to plastics’ end-of-life, an estimated 275 mil- system, resulting in their unintended ingestion posing a lion tons of plastics waste was generated in 2010,6 and risk to humans and wildlife alike. These risks often orig- over 60 percent of that waste is thought to have originat- inate at the time of manufacture, when a range of chem- ed from plastic packaging, which is primarily designed icals including plasticizers, flame retardants, stabilizers, for single use. Globally, plastic waste accounts for over antimicrobials, and antioxidants are used to give plastics 10 percent of landfilled waste by mass. Plastics disposal their unique properties or to enhance their performance. varies widely by region and country, however. In the EU, Common additives such as bisphenol A (BPA), phthalates, of nearly 26 million tons of plastic that reached the waste and polybrominated diphenyl ethers (PBDE), for example, stream in 2014, most went to energy recovery (nearly 40 are known for their potential to act like a hormone in the percent) while nearly equal shares (of around 30 percent) body and may increase cancer and other risks. were recycled and landfilled. That said, landfilling re- One issue is that these substances can leach into mains the number one destination for plastic waste and soils and the environment. In China, the use of plastic the destination for more than half of it in many Europe- agricultural films may be one of the main sources for an countries. China and Indonesia, meanwhile, were the phthalic acid ester contamination in agricultural soils, leading sources of plastic leakage—making them the with concentrations rising roughly one-and-a-half to largest contributors to the 4.8 to 12.7 million tons of plastic threefold in soils under greenhouses or directly covered waste estimated to be entering the ocean each year (as of by films. Uncontrolled emissions from the combustion 2010, see figure 5). While the final destination of agricul- of plastics can also be acutely toxic, carcinogenic, and tural plastics is rather opaque, recycling seems to be lim- endocrine-disrupting when inhaled. Burning has, for ited (possibly around 10 percent in the United States) and example, been a common fate of plastic greenhouse complicated by the presence of pesticide, soil, and hay covers in the Republic of Korea (see figure 2).7 Although residues, as well as the low recycling value of materials emissions vary by substance, burning plastics can emit such as plastic films. In the United States, farms that use a range of gases and fine particles, including persistent, black plastic systems generate 18–22 kg of plastic waste bioaccumulative pollutants such as dioxins, mercury, per hectare, and this waste typically goes to landfills. polychlorinated biphenyls (PCBs), and furans. Whether or not plastics are burnt, a key concern from Impacts a health perspective comes from the tendency for plas- The impact of plastics pollution is not only related to their tics to bioaccumulate within organisms and to concen- composition and form, but also critically with their life trate up the food chain. This makes the ingestion of plas- cycle from manufacture to disposal, and with exposure to tics by animals and wildlife a (toxicological) concern not these. That said, and notwithstanding their tremendous only to the species that are directly affected, but also to versatility and usefulness, the actual use and fate of many higher trophic ones. The ingestion of plastics by marine agricultural plastics is evidently not without harm. Many life is a potential risk to consumers of fish products, for 6 Because it is from a different source and may correspond to a different definition of plastics, this figure cannot be compared directly to the amount of plastic produced. 7 At least as of 2013. Agricultural Pollution Plastics Figure 5: Plastic Waste Leakage 2010 Figure 6: A Mississippi River Fish (U.S.) Source: Jambeck et al. 2015. Permission required for reuse. Source: © Marcus Eriksen. Note: Mismanaged plastic waste generated within 50 km of the coast. Countries in Note: Plastic found inside a fish caught in the Mississippi River, white were not included in the study. United States. instance. And some animal species have been found to ic agriculture, it is “inherently unsustainable.” suffer organ damage from leaching toxins. Plastics can also cause mechanical harm to wildlife Drivers that come into direct contact with them. Plastics can lead One draw of plastics is that they can help save water—as to internal abrasions and gut blockages when ingested when they are used for drip irrigation tape or as a pro- (see figure 6). And when they form heaps of debris in tective soil cover (see figures 8 and 9). In addition to re- which animals get entangled (see figure 7), they can re- taining soil moisture, plastic films, as previously noted, sult in injury and death. Far from being hypothetical, can help keep fertilizer on the field when it rains, sup- these effects are known to be widespread phenomena press weeds, dissuade pests, and retain or deflect heat, as a result of the substantial volumes of plastic waste thus helping farmers to manage the vagaries of weather that can now be found from populated coastlines to and pests, and even extend the growing season. Plastics remote ecosystems and the deep sea. A full 90 percent are very useful to farmers, or are at least perceived to be. of seabirds may be ingesting plastics today, by a 2015 While they represent a recurring expense that farmers study estimate (Wilcox, Van Sebille, and Hardesty). In would rather avoid, they are generally seen as a worth- addition, when plastics form dense patches in bodies of while cost of doing business—one that allows them to water, the algae and plankton that lie in their shadow produce more and higher quality products, and to save (and on which lower trophic species feed) can lack the time and money. In China, plastics (especially films and sunlight they need to photosynthesize, and this too can drip irrigation tubing) have played a central role in al- have ramifications up the food chain. lowing fruit and vegetable production to expand in dry- Notwithstanding the range of technologies plastics land areas. They have also enabled significant (approxi- makes possible or more affordable, and the far-reaching benefits they provide, they can also have some undesirable Figure 7: Marine Debris effects on farms. For example, a flipside of the sought-out warming effect plastics can have on soils—which helps farmers to manage crop seasonality—is that it can disrupt soil biota (privileging bacteria over fungi), with potentially undesirable effects on soil fertility over time. And while the impervious quality of plastic films makes them useful for retaining fertilizer and moisture in soils, it can also increase runoff volumes (by 40 percent), concentrate agro-chemical loads in field runoff, and accelerate erosion (by 80 percent). Because many plastics used in farming have to be pur- chased commercially each growing season, these can rep- resent a substantial monetary expenditure for farms. Black plastic ground coverings, for example, cost U.S. farmers around US$100–120 for the material, and another US$8 for disposal, per hectare. A 2014 Rodale Institute study con- Source: © Ray Boland, National Oceanic and Atmospheric cludes that, although black plastic is allowed within organ- Administration. Agricultural Pollution Plastics Figure 8: Drip Irrigation, a Water-Saving Technology Figure 9: Plastic Mulch Source: © Dripndrip.com. Source: © Fotolia / Chungking. mately 30 percent) gains in cotton and maize yields. universities such as Cornell are working to tackle. The Meanwhile, the repercussions of using plastics are plastic materials used in fields are often an unidentified diverse, diffuse, hidden, and of little direct consequence mix of different resins and additives and may be too for farmers, such that little attention is paid to the aggre- low in value to warrant recycling. In addition to being gate environmental and health effects of plastics use on dispersed in space and bulky, plastic films tend to get an industry-scale. Even where awareness exists, the un- embedded in soils and can require special machinery to derdevelopment of waste collection infrastructure and rid them of moisture, grit, weed seeds, and soil patho- services in many parts of the world represents a hurdle gens. Twine can require hand cleaning to strip off hay when it comes to disposing of plastics more safely. These and grit, though equipment is being developed to tackle and other benefits are touted in commercial advertising these sorts of challenges. Pesticide containers can re- as well as in public extension messaging8 and no doubt quire special treatment to scrub off toxic residues, the reinforced through peer-to-peer learning. In addition, presence of which precludes certain reuses of these, re- while some uses of plastics mainly offer a cost advan- gardless. More generally, the energy, water, and other tage over alternatives (that is, more traditional materi- resources it takes to recycle plastics can, in some cases, als), other plastics offer functionality that other materi- negate its environmental benefits. Nonetheless, agricul- als do not currently offer (at least not affordably). tural plastics recyclers are open for business (see figures 10 and 11). What Can Be Done? Waste-to-energy. Conceptually similar to recycling, Conceptually, the major avenues for mitigating plas- waste-to-energy involves turning plastics into fuel or di- tics pollution involve improving how plastics are man- rectly into energy (through gasification using pyrolysis aged once they enter the waste stream or even further and incineration, respectively). As with recycling, how- upstream during their useful life; reducing how much ever, its effectiveness can be limited by collection chal- is produced, used, or enters the waste stream to begin lenges upstream. Furthermore, its environmental bene- with; lessening their intrinsic potential to cause harm; fit is not unequivocal, as it requires that energy derived and cleaning up after the fact.9 The following represent in either process displace existing and dirtier sources ways to pursue some of these. of energy. This generally implies the use of advanced Recycling. Recycling is one approach to reducing (and costly) emission control technology. Waste-to-en- how much new plastic is produced and how much en- ergy may make the most economic sense in situations ters the waste stream. Plastics have been recycled for of high waste density, a condition that is probably not decades, and a milestone in that regard was the creation met by most agricultural operations, thus limiting the and wide adoption of the Resin Identification Coding relevance of this approach for dealing with agricultural System (RIC).10 In the farming context, however, recy- plastics waste. The conversion of plastics to refuse-de- cling can be impractical and represent a net financial or rived fuel (RDF) for use in manufacturing (for example, time burden for farm operators—issues that agricultural to replace coal in cement production) may be an option 8 An example of the bona fide promotion of plasticulture by an extension service can be found here: https://content.ces.ncsu. edu/plasticulture-for-commercial-vegetables. 9 Cleaning up plastics waste is beyond the scope of this note. Notably, however, the efforts of one organization (The Ocean Cleanup) to deploy a 100 km trash collection system in the Pacific Ocean have drawn attention from both skeptics as well as hopeful scientists and financiers (see figure 14). Soils can be remedied through various processes such as degradation, phytore- mediation, and adsorption. 10 Originally developed by the Society of the Plastics Industry in 1988, the RIC has been administered by the standards orga- nization ASTM International, since 2008. Agricultural Pollution Plastics Figure 10: Silage Wrap Figure 11: Film Recycling Source: © RC Baker Ltd. (recycling company). Source: © Film-recycling.com. in low waste density situations, though only with plas- ing), or avoiding the need for plastics altogether, thus tics of high residual value—hence, probably not with the reducing how much plastic and plastic waste are gener- plastic films used in fields. That said, technical innova- ated. Bans on the open burning of plastics in U.S. states tion may be starting to turn these limitations around.11 have reportedly driven some progress in the design of Materials innovation/biodegradable plastics. more durable farm products, such as plastic covers that Thanks to materials innovation, certain plastics can be can be used for two or more crops before being replaced made biodegradable, thus lessening the likelihood that or more durable greenhouse structures. Plastics pollu- they will persist for a very long term in their plastic tion is very much a design challenge and certain actors state, as they have the potential to be composted or to such as the nonprofit Enviu are treating it as such with photodegrade (or to otherwise degrade). Notably, while initiatives such as the Plastic Fantastic Challenge that bioplastics contain at least some portion of plant-derived aim to mobilize and support the private sector to devise cellulose or chitin, other biodegradable plastics are fos- new solutions (with a focus on plastics in general). In sil fuel-derived plastics which contain additives that can the agricultural context, while some innovations focus accelerate their decomposition under the right condi- on smarter uses of plastics, others involve alternative tions. Materials such as these offer important potential materials, packaged with new technologies or protocols to reduce plastic waste (see figure 12), though they also that address cost and convenience. In the first category, present limitations. Biodegradable plastics can be a nui- Cornell University for instance, has developed farm-lev- sance for recyclers if they are mixed with other plastics, el best practices to improve the recyclability of agricul- and can require special conditions such as commercial composting facilities to actually biodegrade. Depending Figure 12: Biodegrading Plastic Mulch on where they end up, they may not fully decompose or may decompose anaerobically, generating emissions of the greenhouse gas methane. In addition, bioplastics raise a different set of sustainability concerns (pollution, climate, and food security) related to the production and use of their feedstock—though less so when agricultur- al residues are what is being recycled into plastic. From a toxicological standpoint, biodegradable plastics may also have some of the less desirable (for example, endo- crine-disrupting) effects of conventional plastics. Product and process innovation. Both product and process innovation can go a long way toward increas- ing the life of plastics both on and off the farm (that is, Source: © J. Moore-Kucera, Texas Tech University. their durability or potential for reuse), improving their Note: Samples of bioTELO® starch-based plastic mulch recovered after being recyclability (for example, ease of collection and clean- buried in soil for 24 months. 11 The venture-backed company Agilyx , for example, claims to have developed a system to “convert previously non-recyclable and low value waste plastics into crude oil through a patented system that is environmentally beneficial.” Agricultural Pollution Plastics Figure 13: Roller-Crimper Pulled by and research platforms that support smarter uses of Horse and Tractor agricultural plastics and recycling. Funded by the State of Florida, the Southern Waste Information Exchange facilitates recycling by connecting plastics users to recyclers. ➤➤ To the extent that the public sector is involved in the development of sustainability certification standards (for example, organic certification in the United States and Tunisia), it can assess the environmental aspects of plastics use and disposal and shape or influence standards accordingly. ➤➤ To the extent that government also procures farm products more or less directly, it can also use its con- sumer power to shape and influence farming prac- tices. The adjustment of standards allows the market to pay premiums to those who meet them, and may contribute to shifting social norms—or what is con- sidered accepted—when it comes to plastics use. ➤➤ In its capacity as regulator, the public sector can, with adequate enforcement tools, put a stop to the open burning of plastics, or establish rules on the disposal of plastics. ➤➤ Government can invest in waste collection infra- Source: © Yokako Roots Farm (above); © Erin Silva (below). structure and services, and in its procurement capacity, it can set standards on waste management tural plastics. In the second, the Rodale Institute has for services contracted from private sector vendors. example developed a versatile roller-crimper device and ➤➤ To stimulate the materials and process innovation protocols designed to help farmers profitably rely on generally, government can provide selective support cover-crop mulch systems to achieve similar results as to entrepreneurs and business ventures that attempt plastics-based systems without the drawbacks (see fig- to develop business solutions to the public, environ- ure 13). mental challenges posed by rampant plastics use. Improved collection and waste management. The leakage of plastics into the environment can be stemmed by expanding collection, improving waste transport sys- tems to reduce illegal dumping, and closing or upgrad- ing dumping sites located near waterways. When plastic Figure 14: Reality within Reach or Distant Dream? waste is not collected, it is more than twice as likely to leak into the ocean—not to say that collection stems all leakage. Low rates of plastic collection are a major prob- lem, particularly in emerging economies. Forms of support. Public sector support for the above can take on a great many forms. The following are illus- trative. ➤➤ At the highest level, government can advocate for sustainable farming practices and efforts to develop a closed-cycle economy. ➤➤ It can fund scientific, materials, and farm manage- ment research that contributes to the development of safer and more readily reused or recycled plastics, or plastic alternatives. ➤➤ Through support to extension services and other information channels, it can contribute to raising consumer and farmer awareness of and ability to address the challenges of plastics use. In the United Source: © Erwin Zwart / The Ocean Cleanup. States, state funding has allowed agricultural Note: Rendering of the Waste Collection System that The Ocean Cleanup hopes to universities such as Cornell to develop knowledge deploy in the Pacific Ocean in 2020.