The greenhouse gas performance of selected biodegradable and recalcitrant plastics in U.S. landfills

Abstract

Biodegradable plastics are often considered to exhibit superior environmental performance compared to conventional recalcitrant plastics. Here, we assess the greenhouse gas (GHG) emissions of selected biodegradable and recalcitrant plastics made from both fossil and biogenic carbon (C) as disposed in a national average U.S. landfill. This average landfill incorporates consideration of size, precipitation, landfill gas management, and gas collection installation schedule. The GHG emissions of an 80% biodegradable polycaprolactone (PCLf) made from fossil C and a 2% biodegradable poly(butylene succinate) (PBSb) made from biogenic C were evaluated to represent the range of anaerobic biodegradabilities. The 2% biodegradable PBSb has lower GHG emissions than the 80% biodegradable PCLf in the national average landfill. In the best case, which includes aggressive gas collection, conversion of gas to energy, and disposal in a large landfill, the PCLf results in 2423 kg CO2e/mt, which is well above PBSb (−1956 kg CO2e/mt), a hypothetical biogenic and 80% biodegradable PCLb (4739 kg CO2e/mt), and recalcitrant fossil plastic (0 kg CO2e/mt). From a disposal perspective, a recalcitrant biogenic plastic is optimal given the long-term storage of carbon. This study informs the direction of materials research to develop materials that minimize their overall environmental footprint at end-of-life.