Microplastics: The What, Where, Why And Impact

August 23, 2023

Today's guest blog is authored by Craig Coker is a Senior Editor at BioCycle CONNECT and a Principal at Coker Composting and Consulting near Roanoke VA. The original post can be read here.

Among the organics recycling challenges du jour is the potential presence of microplastics in compost and digestate. Two-part article series starts with an overview and ends with findings of current research. Part I


Food waste disposal bans have been implemented in four states (New York, Massachusetts, Rhode Island and Vermont) and diversion requirements are established in six others (California, Oregon, Washington, Connecticut, New Jersey and Maryland). There are also food waste landfill bans and/or diversion policies in a number of communities (San Antonio TX, Boulder CO, Hennepin County MN, Seattle WA and New York City). The oldest of these diversion requirements is in Vermont, which passed its Universal Recycling Law in 2012 and which covers both commercial and residential sources of food wastes.


Over the past 10 years, the organics recycling industry (which includes composting, anaerobic digestion, and diversion to animal feed) has come to recognize that plastics contamination from food packaging is a significant challenge to the implementation and growth of these diversion practices. Plastic packaging is ubiquitous in



the American food distribution system. Many different types of plastics are used in food packaging, as shown in Table 1.

Recovering packaged food wastes for reuse or recycling requires either mechanical depackagers or human labor for source separation, both of which are likely to achieve variable and imperfect separation efficiency (do Carmo Precci Lopes et al., 2019; Edwards et al., 2018). Depackaged and source separated food wastes may contain missorted plastic packaging with varying levels of contamination (Porterfield et al., 2023). Plastic contamination in organics recycling — especially in food waste feedstocks — has led to concerns about microplastics.



What Are Microplastics?

Microplastics (MPs) are small plastic fragments that are less than 5 millimeters (mm) in size — slightly larger than one-eighth inch. A subcategory of microplastics is nanoplastics, synthetic polymers with dimensions ranging from 1 nanometer (nm) to 1 micrometer (μm). For perspective, a compost bacterium is about 1,000 nanometers in size and the width of a single human hair is 20 to 200 μm. Examples of MPs are shown in Figure 1.

There is no consensus on the definition of nano and microplastic particles in relation to human health (Vose, 2022). MPs are directly released to the environment or secondarily derived from plastic disintegration in the environment (Lai, 2022). In a 2021 Spanish study, five polymers represented 94% of the plastic items found in the organic fraction of municipal solid waste: polyethylene, polystyrene, polyester, polypropylene, polyvinyl chloride, and acrylic polymers in order of abundance. Polyethylene was more abundant in films, polystyrene in fragments, polypropylene in filaments, and fibers were dominated by polyester (Edo, 2022).


How Are Microplastics Formed?

MPs can be introduced to agricultural soils through products engineered to be small, such as plastic-coated controlled release fertilizers, treated seeds, and capsule suspension plant protection products. They can be introduced via plastic mulching, contaminated soil amendments, irrigation water, atmospheric deposition, roads and litter (Porterfield et al., 2023 and citations within).

MPs can also be formed during and as a result of food waste depackaging, a separation process. In its simplest form, separation is a binary process, splitting a feed material into two components. These components could be called the extract (or that which you are trying to recover) and the reject (that which you do not want). The objective of a binary materials separator is to split a feed material into two different components by exploiting some difference in the material’s properties.


Separation of materials requires identifying the appropriate characteristic by which separation can be done — or what material property will be exploited to achieve separation. This could be called the “code,” or signal, to tell a machine how to separate materials. The ability of a human or a machine to identify a property’s characteristic and to perform some function, actively or passively, on that material as a result of that information could be called “switching,” or separating the material according to that characteristic (Vesilind, 1984). For example, depackaging commingled food wastes uses density as a code and can use force as a switch to separate packaging, then uses compressive strength (hardness) as a code and pressure as a switch to push organics through an extrusion plate or separator screen.


Depackaging source separated food wastes is very labor-intensive if done by humans. As a result, a number of depackaging equipment systems have come to the U.S. organics recycling market (Coker, 2019; Coker, 2021). The methods used to separate foods from their packages include extrusion (similar to how pasta and ground meat are made), vertical hammermills (force applied against a vertical punch-plate screen), horizontal paddle separators (squeezing the packaging between paddle and containment shell), and centrifugal force separators. There are no data available on which depackaging methods produce MPs or in what quantities, but it is reasonable to assume that machines exerting more force on packaged foods risk higher production of MPs due to shattering of brittle plastics like some high-density polyethylene (HDPE ) and polypropylene.


Health Effects of Microplastics

The research on the health effects of microplastics has focused, to date, on direct exposure. MPs in composts and digestates used as soil amendments are a secondary pathway of exposure, which has not yet been studied to any extent.


Inhalation and ingestion are the two primary routes of exposure to MPs. Inhalation causes physical damage to the lungs and ingestion is thought to have potential impacts on the immune system, liver, energy metabolism and reproduction. There are no comprehensive studies of MPs in the diet, although MPs have been found in seafood/fish, salt, beer, honey, milk, rice, sugar and seaweed (Vose, 2022).


In 2019, the World Health Organization (WHO) commissioned a report to evaluate the evidence of risks to human health associated with exposure to nano and microplastic particles (NMP) in drinking water. A key observation is that MPs are ubiquitous in the environment and have been detected in environmental media with direct relevance for human exposure, including air, dust, water, food and beverages.


There is increasing awareness of the occurrence of MPs in air and their implications for human health. Studies of the inhalation of MPs should include consideration of their biokinetics, as their intake depends on their size, shape, density and surface chemistry, which influence their deposition in the alveolar regions of the lungs. Better characterization is needed of the properties of MPs in air, such as the fractions that contribute to airborne particulate matter and their absolute concentrations. The current lack of such data limits characterization and quantification of the impact of human inhalation of MPs.


Ingestion of MP has been reported in a variety of foods and beverages. An assessment of overall human exposure to MPs is complicated by the limited availability of data on the occurrence of MPs measuring <10 μm in water, food and beverages. Observations from particle and fiber toxicology indicate that particles <10 μm are probably taken up biologically. Most of the available studies on the occurrence of MPs in water, food and beverages reported particles measuring >10 μm, which are unlikely to be absorbed or taken up.


The WHO assessed the quality, reliability and relevance of data on both exposure and effects for their possible contribution to a risk assessment of MPs. The assessment scores indicated that the available data are of only very limited use. Several shortcomings were identified, the most important of which was the heterogeneity of the methods used. It is recommended that standard methods be developed and adopted to ensure that the research community can reduce uncertainties, strengthen overall scientific understanding and provide more robust data for assessing the risks of human exposure to NMPs (WHO, 2022).


Environmental Effects of Microplastics

MPs are categorized as emerging persistent pollutants that occur widely in various ecosystems. MP measurements reported in the literature are 10’s to 1,000’s of particles per dry kilogram of agricultural soils, similar to levels found in composts and digestates (Porterfield et al., 2023). Microplastics in soils have been found to increase soil aeration, water repellence and porosity but to decrease soil bulk density and aggregate sizes (e.g., de Souza Machado et al., 2018b, 2019; Kim et al., 2021; Qi et al., 2020).


MPs’ impacts on terrestrial plants (particularly crops) are poorly understood. Given the persistence and widespread distribution of MPs in the soil, they have potential impacts on terrestrial plants (Wang et al., 2022). Due to their small size and high adsorption capacity, MPs can adhere to the surfaces of seeds and roots, and thus inhibit seed germination, root elongation, and absorption of water and nutrients, and ultimately inhibit plant growth. MPs, especially nanoplastics, can be absorbed by roots, and be moved to stems, leaves, and fruits. The adherence and accumulation of MPs can induce oxidative stress, a complex chemical and physiological phenomenon that occurs in higher plants (vascular) and develops as a result of overproduction and accumulation of reactive oxygen species. They also can induce toxicity to plant cells and to genetic material in plants, leading to a series of changes in plant growth, mineral nutrition, photosynthesis, toxic accumulation, and metabolites in plants tissues. Overall, the phytotoxicity of MPs varies dependent on their polymer type, size, dose and shape, plant tolerance, and exposure conditions. The accumulation of MPs and subsequent damage in plants may further affect crop productivity, and food safety and quality, causing potential health risks (Wang et al., 2022).


Soil microorganisms can be affected by MPs. There are effects on species dominance, diversity and richness reported in the literature (e.g., Blöcker et al., 2020; Fei et al., 2020; Ren et al., 2020) and MPs have been found to cause oxidative stress and abnormal gene expression in earthworms (which can consume and transport MPs) (Cheng et al., 2020).


Even compostable plastics can be a source of MPs. Not all certified compostable packaging fully composts in all facilities due to variability in the technologies and processes used at each facility (USEPA, 2021). The European compostable plastics standard (EN 13432) defines a material as compostable, if 90% (by weight) of the material is fragmented (disintegrated) into particles <2 mm, i.e., below the limit at which particles “count,” after 12 weeks of standardized composting and fully mineralized by 90% within 6 months. The remaining 10% may be transformed into biomass or simply be fragmented into microplastic (Steiner, 2022).

 

Disclaimer: Guest blogs represent the opinion of the writers and may not reflect the policy or position of the Northeast Recycling Council, Inc.


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By Megan Quinn | WasteDive July 8, 2026
A resurgence of secondhand shopping, new sorting methods and policy initiatives are all poised to help shift the needle on textile waste, speakers at a NERC webinar said. Thrift stores are a first line of defense against textile waste, and changing attitudes about thrifting and resale could help shape recycling systems and divert more material from landfills in coming years, said speakers at the Northeast Recycling Council’s material reuse forum webinar on Tuesday. Secondhand clothing is playing a powerful role in U.S. textile export markets, which in turn influences how and when textiles end up in recycling streams, said executives from thrift stores and researchers from the National Institute for Standards in Technology. A rising interest in thrifting, upcycling and clothing repair could help keep clothing in use longer, and when textiles are too worn out to wear, newer sorting technologies could help sort end-of-life textiles more effectively for better end markets, they said. Here’s a few takeaways from the webinar: Thrift stores: making landfill diversion look cool Thrifting is not a new concept, but Americans have become more and more receptive to thrifting in recent years due to a combination of rising expenses, tariff concerns and economic uncertainty. There’s also the lasting effects of the COVID-19 pandemic, when people had more time to look through their closets for unwanted items to donate, said Giana Manganaro Cronin, associate director of retail for More Than Words, a nonprofit youth job training program in the Boston area. More Than Words uses its thrift stores as a key way to offer job training and provide stable jobs for the youth who participate in the program, she said. The organization used to sell used books, but a fresh wave of interest in secondhand shopping spurred by the pandemic prompted the nonprofit to switch to a thrift store model instead. “This was not only a crucial pivot for the environment and to keep more things out of the landfill, but also do well for our business and our young people too,” she said. The nonprofit’s thrift stores, called Boomerangs, offer a 98% margin compared to its previous 62% retail bookstore model, and Manganaro Cronin expects that to continue in coming years. Gen Z shoppers are leading the trend, in part because reducing their environmental footprint is a core value for the demographic, she said. About 64% of shoppers in that age range look at resale options before buying new products, she said. Young shoppers are expected to continue influencing this trend, said Uli Stosch, chief officer of strategic development for Planet Aid, a thrift store nonprofit that has collected and reused more than 2 billion pounds of clothing since its inception in 1997. Citing numbers from an annual resale report prepared by online thrift company ThredUp, she added that the U.S. secondhand apparel market grew 14% in 2024, and the market is anticipated to reach $74 billion by 2029. The next step: Labor-intensive export and recycling markets More Than Words and other thrift stores like it does its best to sell as many items as possible. But for items that can’t sell, the organization often partners with secondary buyers, such as wholesalers who have access to a broad range of additional secondhand markets, Manganaro Cronin said. Stosch said thrift stores and other secondhand stores typically sell between 10% and 50% of their items, and a “small amount’ ends up going in the trash — mostly soiled items not fit for wearing or using. Another portion gets classified as “mixed rags” and baled for export, where they are further sorted for more reuse, resale or recycling purposes, she said. Many of these bales end up in Pakistan and Malaysia, where workers are trained to go through the time-consuming process of hand sorting each piece to separate out the quality clothes for resale while setting aside lower-quality textiles for other uses. “It’s very, very labor intensive to do this. You stand for long hours and have to pick through all the right things,” she said. Because it takes so much time to sort these items correctly, “there’s a limit to how much textiles we can process this way,” she said. From there, many of the clothes destined for resale go to countries in Africa, the Caribbean and Central America. More than 1.5 billion people around the world rely on second-hand clothing, she said, especially as an alternative to low-quality fast fashion brands. Guatemala has a particularly strong secondhand import market, she said. A 2025 study from Full Cycle Resource noted that the country imported 290 million pounds of clothing in 2023 and reused more than 91% of it, with women-owned clothing stores making up more than half of the industry. Complex streams, complex recycling options When clothing or textiles are too worn out or unfit to be worn again, and have already been downgraded to be used as rags or industrial cloth, recycling is one of the next best options. That’s when a new set of challenges kick in, said Katarina Goodge, a materials research engineer at NIST. Textiles are a complex and challenging waste stream to sort, in part because there are no set standards on how to handle the materials today, she said. Setting standards “would help scale up in efficiency in this system,” she added. Another problem: Textile sorting is largely done by hand, as opposed to other recycled materials that can quickly be sorted by a range of AI-enabled robotic sorting technologies, Goodge said. One reason hand sorting is the norm is because it’s tough to tell exactly what a garment is made of. “We need to know the fiber content to know how to recycle that garment,” she said, but the tag inside might simply say it’s made of 95% rayon and 5% “other.” A particularly itchy tag might get cut out of the garment entirely. “We need to look at a more systematic and technological solution to this,” she said – and technology is catching up. Handheld near-infrared devices can give insight into a garment’s material makeup, and when paired with AI or machine learning models, identifying fiber contents can become faster and more efficient. A handheld NIR scanner could be paired with hand sorting to guide garments into the right bins, Goodge said, and larger-scale solutions might be able to identify textiles while they’re on a conveyor belt, with a robotic arm component to pick off specific items. In the U.S., textile recycling infrastructure is not as common as recycling systems for curbside materials, though some companies have invested in such technology in recent years. A future of reuse, repair and policy change Legislation could make a difference in textile recycling initiatives in coming years, the speakers said. California’s extended producer responsibility for textiles law is in the process of being implemented, which will prompt more outlets for clothing donation, repair and recycling, Stosch said. Countries in the EU are also on the hook to implement similar textile EPR programs. Meanwhile, disposal bans in states like Massachusetts have prompted both thrift stores and lawmakers to wonder what to do with textiles that aren’t fit for resale but could be recycled into other products, Stosch said. Most thrift stores will accept apparel that’s torn or missing buttons, as long as it’s clean: “If it’s clean, it can be made into something else.” There’s also more room for creative ways to reuse or repair clothing before it goes to a recycling center, speakers added. For example, community repair events are good ways to teach basic sewing skills and inspire people to make something new with old apparel, Goodge said. “We used to have some infrastructure in the U.S. for repair, and that has largely sort of gone away, because it’s really hard to keep that economically viable,” she said. Yet repair efforts “have a huge potential to keep a lot of these garments as garments.” Read on WasteDive.
By IndexBox July 8, 2026
Thrift stores act as a frontline barrier against textile waste, and shifting consumer perspectives on thrifting and resale could help refine recycling systems and pull more material away from landfills in the years ahead, according to panelists at a Northeast Recycling Council material reuse forum webinar held on Tuesday. Executives from thrift stores and researchers from the National Institute for Standards and Technology pointed out that secondhand clothing holds a strong position in U.S. textile export markets, which in turn shapes how and when textiles reach recycling streams. A rising enthusiasm for thrifting, upcycling, and clothing repair could extend the useful life of garments, and when textiles become too worn for wear, emerging sorting technologies could more efficiently handle end-of-life textiles to improve end markets, they noted. Thrift Stores: Making Landfill Diversion Attractive Thrifting is not a novel idea, but Americans have grown increasingly open to it in recent years due to a mix of rising costs, tariff worries, and economic instability, along with lingering effects of the COVID-19 pandemic, when people had extra time to sort through their closets for items to donate, said Giana Manganaro Cronin, associate director of retail for More Than Words, a nonprofit youth job training program based in the Boston area. More Than Words leverages its thrift stores as a primary means to deliver job training and secure stable employment for participating youth, she explained. The organization previously sold used books, but a surge in interest in secondhand shopping triggered by the pandemic led the nonprofit to adopt a thrift store model instead. This shift was not only vital for the environment and for keeping more items out of landfills, but also beneficial for the business and the young people involved, she said. The nonprofit's thrift stores, known as Boomerangs, achieve a 98% margin compared to the previous 62% margin from its retail bookstore model, and Manganaro Cronin anticipates this trend will persist. Gen Z shoppers are driving this movement, partly because minimizing their environmental impact is a fundamental value for that group, she noted. About 64% of shoppers in that age bracket explore resale options before purchasing new items, she added. Young consumers are expected to keep shaping this trend, said Uli Stosch, chief officer of strategic development for Planet Aid, a thrift store nonprofit that has gathered and reused over 2 billion pounds of clothing since its founding in 1997. Drawing on data from an annual resale report by online thrift company ThredUp, she noted that the U.S. secondhand apparel market expanded by 14% in 2024 and is projected to hit $74 billion by 2029. Labor-Intensive Export and Recycling Markets More Than Words and similar thrift stores strive to sell as many items as possible, but for unsellable goods, the organization frequently collaborates with secondary buyers such as wholesalers who have access to a wide array of additional secondhand markets, Manganaro Cronin said. Stosch noted that thrift stores and other secondhand retailers typically sell between 10% and 50% of their inventory, with a minor portion ending up in the trash, mainly soiled items unsuitable for wearing or use. Another share is categorized as mixed rags and baled for export, where it undergoes further sorting for reuse, resale, or recycling. Many of these bales are sent to Pakistan and Malaysia, where workers are trained to manually sort each piece to separate quality clothing for resale while diverting lower-quality textiles for other uses. Stosch described this process as extremely labor-intensive, requiring long hours of standing and sorting through items, and noted that there is a cap on how much textiles can be handled this way due to the time involved. From there, many clothes intended for resale are shipped to countries in Africa, the Caribbean, and Central America. Over 1.5 billion people globally depend on secondhand clothing, she said, particularly as an alternative to low-quality fast fashion brands. Guatemala has a notably strong secondhand import market, she added. A 2025 study by Full Cycle Resource found that the country imported 290 million pounds of clothing in 2023 and reused more than 91% of it, with women-owned clothing stores accounting for over half of the industry. Complex Streams, Complex Recycling Options When clothing or textiles are too worn or unfit for further wear and have already been downgraded to rags or industrial cloth, recycling becomes one of the next best options. This is where a fresh set of difficulties emerges, said Katarina Goodge, a materials research engineer at NIST. Textiles represent a complex and challenging waste stream to sort, partly because no established standards exist for handling these materials today, she said. Establishing standards would help boost efficiency in this system, she added. Another issue is that textile sorting is predominantly done manually, unlike other recycled materials that can be quickly sorted using various AI-enabled robotic sorting technologies, Goodge noted. One reason manual sorting remains standard is the difficulty in determining a garment's exact composition. Goodge explained that knowing the fiber content is essential to know how to recycle a garment, but the tag inside might only state it is made of 95% rayon and 5% other, or an itchy tag might be completely removed. She emphasized the need for a more systematic and technological approach, and noted that technology is advancing. Handheld near-infrared devices can reveal a garment's material composition, and when combined with AI or machine learning models, identifying fiber contents can become faster and more efficient. A handheld NIR scanner could be used alongside manual sorting to direct garments into appropriate bins, Goodge said, and larger-scale systems might identify textiles while on a conveyor belt, with a robotic arm component to pick out specific items. In the U.S., textile recycling infrastructure is less common than curbside recycling systems, though some companies have invested in such technology in recent years. A Future of Reuse, Repair, and Policy Change Legislation could drive changes in textile recycling efforts in the years ahead, the speakers said. California's extended producer responsibility for textiles law is being implemented, which will encourage more outlets for clothing donation, repair, and recycling, Stosch said. Countries in the EU are also required to implement similar textile EPR programs. Meanwhile, disposal bans in states like Massachusetts have led both thrift stores and lawmakers to consider what to do with textiles that are not suitable for resale but could be recycled into other products, Stosch said. Most thrift stores will accept apparel that is torn or missing buttons, as long as it is clean, she noted, adding that if it is clean, it can be turned into something else. There is also potential for creative ways to reuse or repair clothing before it reaches a recycling center, speakers added. For instance, community repair events are effective for teaching basic sewing skills and inspiring people to create something new from old apparel, Goodge said. She noted that the U.S. once had some infrastructure for repair, but that has largely disappeared because it is difficult to keep economically viable, yet repair efforts have significant potential to keep many garments as garments. P Read on IndexBox.
By Chris Voloschuk | Recycling Today July 3, 2026
The Northeast Recycling Council (NERC), Brattleboro, Vermont, recently released its “ Northeast Flow of Glass Report ,” a regional analysis looking at glass container generation, collection, recycling, disposal, policies and end markets across the 11 states in the 11 Northeast states. The report was developed by NERC’s Glass Committee with support from state agencies, industry partners and stakeholders across the region and builds on the organization’s previous research into glass recovery, processing and end markets. NERC says it is meant to provide a comprehensive snapshot of how glass moves through the Northeast materials management system and highlights opportunities to strengthen glass recycling through policy, infrastructure investment and market development. According to NERC , key findings in the report include: Vermont (79.9 percent) and Connecticut (77 percent)—two states that operate deposit return systems (DRS)—recycled the highest share of glass containers relative to total glass container scrap generated. Connecticut led the region in per capita glass collection at 65.8 pounds per resident. New York collected the greatest total tonnage of glass containers for recycling at 281,065 tons annually, followed by New Jersey with approximately 197,000 tons. Five states in the region operate DRS programs that include glass beverage containers. All Northeast states provide residents with access to curbside and/or drop-off recycling programs. Reporting methodologies vary significantly among states, affecting direct comparisons of recycling performance. Recycled glass supports multiple end markets, including new containers, fiberglass, concrete applications and aggregate products. “Glass is one of the few packaging materials that can be recycled repeatedly with minimal loss of quality,” says NERC Executive Director Megan Schulz-Fontes. “The data show that strong collection systems and supportive policies can significantly increase glass recovery and create valuable feedstock for manufacturers.” NERC says its findings demonstrate that opportunities exist across the region to increase glass recovery through improved collection systems, stronger processing infrastructure and continued end market development. It also claims its analysis reveals “substantial variation” in state reporting methodologies, recycling requirements and collection systems. Per the report, while all Northeast states provide residents with access to curbside and/or drop-off programs, collection models differ considerably. Five states operate DRS programs, several off source-separated glass drop-off programs and Pennsylvania is the only state identified as providing source-separated curbside glass collection in select communities. NERC says these differences present challenges when comparing data across states and highlight the need for continued efforts to improve reporting consistency and transparency. The report notes that recycled glass serves a growing number of end markets, including new glass containers, fiberglass insulation, pozzolan for concrete, foam glass aggregate and other construction applications. “Many of these markets require high-quality glass cullet with low contamination levels, making effective collection and processing systems essential,” NERC writes. Although glass is heavier than many alternative packaging materials and can be more transportation-intensive when moved long distances, NERC reports that increasing local and regional collection, cleaning and processing capacity can improve environmental outcomes. The organization says recycled glass can help reduce greenhouse gas (GHG) emissions associated with manufacturing by replacing virgin materials and supporting a more circular economy. NERC says its findings suggest that strategic investments in collection systems, processing infrastructure and end market development could increase glass recovery rates throughout the Northeast while supporting resource conservation, economic development and reductions in GHG emissions. Read on Recycling Today .