Characterization of plastic contamination entering food waste management and implications for food system impacts

Abstract Managing food waste (FW) by composting and anaerobic digestion offers potential sustainability benefits compared to conventional disposal practices. However, these processes can be unintended sources of plastic pollution to the environment, due to the presence of plastic contaminants originating upstream in the food system. During FW processing, plastic contaminants may partially degrade, ultimately leading to microplastic releases by way of agricultural use of compost and other bio-based products. Preventing and managing these releases requires a better understanding of the sources, magnitude, and nature of plastic contaminants traveling through FW management systems. This research collected representative FW samples from common generators, including restaurants, groceries, schools, and households, characterized the abundance, type, and material composition of contaminants present, and interpreted results through the lens of potential economic and ecological risks. Contaminants were observed in 80% of FW samples and were predominantly composite plastics, including multi-layer films, plastic-coated paperboard, and mixed polymer containers. The most common contaminants observed were fruit and vegetable stickers (30% by item count), but their small size and light weight make an insignificant contribution to total contaminant mass (<1%). The majority of contaminants were thin, flexible items, including plastic wraps, bags, gloves, and containers, which present added challenge to FW management due to the potential to impede mechanical equipment and reduce the production and quality of compost products. These results offer insights into potential strategies, including education, policy, and technology development, that can be leveraged across the FW management system to prevent contamination and improve food system sustainability.