Does Composting Food Scraps Add Microplastics to Soil?
A new UVM study on national food waste recycling has a climate win and a real catch.
Key takeaway: No, composting food scraps doesn't add microplastics on its own; the plastic comes from packaging and stray items mixed in with the scraps, not the food itself. A new University of Vermont study in Nature Food found that recycling food waste nationally could cut its climate impact by up to…
By Dear Sarah · · Updated
Key takeaways
- A University of Vermont study published in Nature Food found that diverting U.S. food waste from landfills to composting and anaerobic digestion could cut its climate impact by 89 to 99%.
- The same national-scale shift could reduce nitrogen pollution by 49 to 54% and phosphorus pollution by 78 to 98%, both major drivers of algal blooms.
- Without better packaging and sorting, the researchers estimate roughly 20,000 tons of plastic could end up in U.S. farmland soil annually through contaminated compost.
- Lead author Kate Porterfield said plastic contamination in the food system is 'literally everywhere' and that even careful sorting lets a small amount through.
- Individuals composting at home aren't the contamination source; removing produce stickers, twist ties, and non-certified 'compostable' bags before scraping food into a bin closes much of the gap.
Short answer: no, not in the way that should make you toss your compost bin. A new national study out of the University of Vermont found that recycling food waste instead of landfilling it could cut its climate impact by up to 99%. The catch is real too. Without better sorting and packaging, that same system could send up to 20,000 tons of plastic into American farmland every year. Both things are true at once, and knowing that actually makes composting easier to do well, not harder to trust.
Does composting actually add microplastics to soil?
It can, but not because of the food scraps themselves. The plastic comes from what's mixed in with them: produce netting, twist ties, the thin film on a "compostable" takeout container that isn't actually certified compostable, or the plastic liner someone forgot was there. Postdoctoral researcher Kate Porterfield at the University of Vermont's Gund Institute for Environment, who led the new analysis published in Nature Food, put it plainly: plastic contamination in the food system is "literally everywhere." Even with people and machines sorting it out, she said, "a small amount sneaks through. And if you're talking about very, very large amounts of food waste, that can add up."
What did the new food waste study actually find?
Porterfield and senior author Eric Roy, who directs UVM's Casella Center for Circular Economy and Sustainability, modeled what would happen if the U.S. diverted food waste from landfills to composting and anaerobic digestion at a national scale. The upside is enormous: an 89 to 99% cut in climate impact, plus a 49 to 54% drop in nitrogen pollution and a 78 to 98% drop in phosphorus pollution, the kind of runoff that fuels algal blooms in lakes and rivers. The risk is that spreading the resulting compost on farmland could carry roughly 20,000 tons of microplastics into U.S. soil each year if packaging and sorting don't improve alongside it. Roy's takeaway wasn't "stop composting." It was that the U.S. needs to plan this at a national scale the way Vermont, a state that already bans landfilling food scraps, has started to. "We thought, we need to think about this at a big scale," he said, "because Vermont's leading on this issue."
This is the same pattern researchers keep finding wherever plastic meets a well-intentioned system. Sarah's written before about how much microplastic one laundry load actually sheds and what "living plastic" could mean for ending microplastics for good. The lesson is consistent: the fix usually isn't "do less." It's "sort better, source cleaner, and demand the packaging catches up."
Why this matters for you
If you scrape your dinner plate into a countertop bin, drop food scraps at a farmers market collection point, or pay for curbside compost pickup, you are already part of the system this study is describing. That's a good thing to keep doing. The study isn't telling women who compost to stop; it's telling cities, states, and packaging companies to get their act together before this scales nationally. You're not the contamination source. The plastic clamshell your lettuce came in is.
Where you do have real power is at the sorting step, the exact place Porterfield's research says plastic sneaks through. A woman scraping her own kitchen bin catches things a sorting facility misses: the twist tie still wrapped around herb stems, the produce sticker on an apple core, the "eco" bag that's actually just tinted plastic. It's the same instinct behind the boatful of women currently mapping ocean plastic in real time — someone has to be the one who actually looks closely, and that habit adds up across a whole system.
One thing to try today
Before your next scrape into the compost bin, do a 10-second check: pull off produce stickers, twist ties, and rubber bands, and skip any bag that isn't certified compostable (look for the BPI or "OK Compost" logo, not just the word "eco" or "green" on the packaging). That's the exact gap Porterfield's research points to, and it's one you can close in your own kitchen tonight.
Quote to sit with
"It's the little things citizens do. That's what will make the difference. My little thing is planting trees." — Wangari Maathai
💌 Sarah
Frequently asked questions
Is composting bad for the environment because of microplastics?
No. The new UVM research found composting and anaerobic digestion still deliver a massive net climate win, up to a 99% reduction in food waste's climate impact. The microplastic risk is a real but separate problem tied to contaminated packaging, not to composting itself, and it's fixable with better sorting and packaging standards.
Where do microplastics in compost actually come from?
They mostly come from plastic packaging mixed in with food scraps, things like produce netting, twist ties, produce stickers, and takeout containers or bags that aren't certified compostable. Sorting facilities and machines remove most of it, but researchers found a small percentage consistently slips through, which adds up at national scale.
How do I know if a compostable bag is actually compostable?
Look for a certification logo like BPI (Biodegradable Products Institute) or 'OK Compost' printed on the packaging. Words like 'eco-friendly,' 'green,' or 'plant-based' on their own aren't a guarantee; they're marketing language, not a certification.
Should I stop composting my food scraps?
No. Researchers Kate Porterfield and Eric Roy at the University of Vermont aren't recommending less composting, they're calling for national planning so packaging and sorting keep pace as more food waste gets diverted from landfills. Home and curbside composting are still one of the highest-impact eco habits available to an individual.
What state is leading on food waste and microplastic policy?
Vermont, which already bans landfilling food scraps statewide, is cited in the study as the model other states and the federal government should look to as food waste recycling scales up nationally.
Sources
- Food waste recycling in the USA can reduce climate and nutrient pollution impacts yet risks plastic accumulation in soils — Nature Food
- Recycling food waste is good for the climate, but could add microplastics to soil, study finds — WBUR News
- Recycling Food Waste Would Bring Huge Benefits, But Microplastics a Challenge — UVM Gund Institute for Environment
Keep reading
- What Is 'Living Plastic' and Could It End Microplastics? — A scientist just built plastic that destroys itself in six days with no microplastics left behind. Here's how, and why it matters more than another straw ban.
- Does Plastic Free July Actually Make a Difference? — Two weeks into Plastic Free July and already slipped? Here's the data on why it still counts.
- How much microplastic does one laundry load actually shed? — One load of laundry can shed 700,000 microfibers. Six low-lift changes that actually keep them out of the water, starting with your next wash.
- Did Amazon Deforestation Really Drop to a 10-Year Low? — Amazon deforestation just hit its lowest point in a decade. Here's why that's real, and why the women tracking it aren't celebrating yet.