 Examples of some of the certified compostable materials that Black Earth Compost accepts from its customer, Cabot Theater in Beverly, Massachusetts. The theater composts all popcorn bags, cups, straws and napkins and recycles. All drinks are served in compostable cups. Credit: Lisa Champigny While some report that compostable items like cutlery don’t break down well, the Composting Consortium’s field study found that, for the most part, compostable packaging does fully decompose at industrial facilities. Eight of nine composters studied that accepted compostable packaging had no detectable amounts of the materials in their finished compost. “When [compost] piles have optimum conditions with the best management practices, bioplastics by and large break down very well,” Rhodes Yepsen, an executive director at BPI and a member of the Composting Consortium, told EHN. That’s Black Earth Compost’s experience. “After three months, there s no more compostable plastic,” Dong said. “Any plastic that you see past that point within the life of a pile, that s conventional plastic.” However, in compost samples University of Vermont researchers studied, they found fragments of poly-lactic acid, or PLA, which is commonly used to make compostable packaging, and what appeared to be compostable bags but could have been look-alikes. Though they weren’t the majority of plastics found, they were “wellrepresented,” Kate Porterfield, a doctoral student at the University of Vermont, told EHN. More troubling, the University of Vermont’s research found widespread microplastic contamination in compost materials, though that research didn’t distinguish whether the microplastics came from compostable or traditional plastic materials. Roy said, “it s a tricky question” what happens to microplastics created by compostable materials. “Theoretically, they will persist in the environment for a shorter amount of time than traditional plastics will,” and that’s a “good thing.” But there’s “some evidence that these materials are not necessarily entirely benign in the soil environment.” Degradation of microplastics “all depends on what the polymer is, how it s put together and the environmental circumstances,” Richard Thompson, professor of marine biology and director of Plymouth University’s Marine Institute, told EHN. Meanwhile, studies show that chemical additives or chemicals transported by microplastics, may be more concerning than the plastic polymers themselves, which complicates our understanding of risk. “All the combinations of polymer, additive, shape and size…each might have different effects in the soil environment,” Roy said. That is perhaps why Franciosi said that, after PFAS, “microplastics are the next fire” for the compost industry.
PFAS and other chemicals
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