Getting plastic out of compost

Composting diverts organic waste from landfills, recovers nutrients, and reduces methane emission. However, plastic contamination is a growing problem as composting programs expand, and fears of plastic pollution discourage farmers from applying compost to their fields. No standard protocol exists for detecting and measuring plastic contamination across the full range of particle sizes. This project will develop that protocol for use at commercial compost facilities, and test two methods of plastic removal: heating it to high temperatures to break down plastic into biochar, a carbon-rich material that can be applied to soil, and introducing earthworms to biologically degrade plastic. Working in close collaboration with leading composters across California’s Salinas Valley, a interdisciplinary team of soil scientists, environmental engineers, and epidemiologists aims to make composting safer and expand its agricultural use.

Above: Disposal of biodegradable kitchen waste into compost bin. Image credit: Milos Ruzicka / iStock