Municipal composting programs are failing because consumers put plastic bags, stickers, and packaging into green bins, contaminating entire batches

Cities across the United States are rolling out residential food scrap composting programs to divert organic waste from landfills. The problem is that residents do not know -- or do not care -- what can go in the green bin. A 2024 report by the Composting Consortium found that conventional plastic is the number one contaminant of compost feedstock at facilities accepting food scraps. Even with current best practices and up to 95% contamination removal rates, 40% of surveyed composting facilities still end up with trace amounts of conventional plastic in the finished compost. One resident tossing a plastic bag of food scraps instead of emptying the scraps loose can contaminate an entire truckload. The consequence is that compost facilities produce lower-quality compost riddled with microplastic fragments, which then gets spread on farmland and gardens, introducing plastic pollution into soil and potentially the food supply. When contamination rates get too high, facilities reject incoming loads entirely, sending them to landfill -- the exact outcome the composting program was designed to prevent. Farmers and landscapers who buy compost are increasingly demanding plastic-free certification, which many municipal programs cannot provide. The problem persists because of a fundamental design flaw in curbside composting: it relies on millions of individual households to sort correctly, with no enforcement mechanism. A recycling bin with a plastic bottle in it is obvious; a compost bin with a produce sticker, a "compostable" bag that is actually not commercially compostable, or a rubber band around a bunch of broccoli is nearly invisible. Education campaigns help but have diminishing returns. Washington State passed new rules in 2024 to reduce plastic contamination in compost, but enforcement at the household level is essentially impossible. The technical solution -- optical sorting and screening at facilities -- adds $2-5 per ton in processing costs that many municipal programs cannot absorb.