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Composting and Microplastics: What Can Be Done? 

5 min read

How do we know if there is plastic in our compost? Studies show there is microplastic in many environments and living creatures (including us!). We release microplastics in our own lives by cutting, tearing, and twisting plastic bags to open them. 

Luckily, there are some ways to help reduce how much microplastics end up in our backyard and community compost. 


Understanding Microplastics 

Most materials in nature can break down into smaller parts by being consumed by animals, plants, fungi, bacteria, or by being broken down through weathering and erosion. Some parts of plastic do break down like other naturally-occurring substances, but other parts break off into smaller plastic pieces called microplastics (plastics smaller than 5mm). 


These microplastics are small enough to leak out into the environment with wind, rain, and leakage (called leachate) from biodegradation (like composting). They can get into the soil, into groundwater, and be absorbed into the bodies of animals that eat or drink from contaminated sources, where they can accumulate to dangerous levels. They can also contain heavy metals or other toxins.


Currently, there is no clear way to remove all these microplastics from the soil or compost. Testing for microplastics levels in soil is still being worked on, and methods and results are not always consistent across labs. 


The Who, What, Where of PFAS, PFOA, and PFOS 

PFAS (per- and polyfluoroalkyl substances) are a group of chemicals found in many of our plastic products. They help make products more resistant to water, grease, stains, and heat. 


A large source of PFAS in the environment is from big operations like textile (clothing) and paper factories and from industrial areas. They are also in some firefighting foams, and also in our anti-stain consumer waste like non-stick cooking pans. 


Science today has talked a lot on two types of PFAS: PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid). They are a concern to the health of the environment and us because of their ability to accumulate in an organism’s body. High levels of PFAS may contribute to adverse health conditions, but we don’t know what consistent exposure to low levels does. 


The Good and Bad of Bioplastics

Bioplastics are made from natural resources like corn, and they behave like fossil fuel-based plastics when processed. They can decompose but only if disposed of correctly, and it still takes a long time so it is not recommended for backyard or small community composting. Scientists are not sure if bioplastics create their own micro-bioplastics, but have noted that it is difficult to create bioplastics to be both biobased (made from raw materials like plants) and biodegradable (breaks down like natural materials). 


Community Composting Can Help Reduce Microplastics in Compost

Plastic in compost can come from accidentally putting things like produce stickers, plastic containers, and non-biodegradable silverware into the compost. 


Larger composting facilities take tons of food and yard waste from many people by picking up their compost bins, which means there is more chance of plastic contamination. Since larger operations use machines like tractors to move and mix huge amounts of food waste, it is much harder to accurately sift through the food waste to spot and remove any plastic non-food items.   


Backyard and small–scale community composting projects allow people to know what goes into the compost. We can work together to better avoid plastic contaminants from the get-go with community education, workshops, and outreach. Composters can also collect and sort through the containers of food waste before they are put into the community’s composting system. The smaller scale allows people to address and adapt around issues of plastic sources as they come up. 


We can also work together to avoid or reduce use of first-source plastic. By buying, trading, and sharing items that are reused and recycled, less new plastic needs to be created. This helps limit how much plastic will end up in trash and landfills, and slows how much washes into our waters and land. 


Quick Tips for Reducing Microplastics in Our Compost

  • Take off produce stickers from your fruits and veggies before you add kitchen scraps to your compost. 

  • Use non-plastic bags at the grocery store to hold your produce.

  • Avoid composting tea bags unless they are marked as being plastic-free. Try loose leaf tea with filters made of wood/plants or use a metal diffuser instead.

  • Use reusable coffee pods if you use a coffee machine like a Keurig. Scoop out the coffee grounds for backyard composting.

  • Avoid composting laundry lint. Most clothing today has some form of plastic in it.

  • Avoid composting any paper products with plastic-coatings.

  • If possible, using composting systems that aren’t made with plastic like keyhole gardens, bin systems, worm bins in wooden containers, or making a compost pile if you have the space.


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