Thermophilic anaerobic biodegradation of commercial polylactic acid products

This study examines the anaerobic biodegradability of six commercial polylactic acid (PLA) products under thermophilic conditions. All products showed similar methane yields of 507 ± 24 L CH₄ kg^-1 VS, with an estimated biodegradability of 100 %. However, these products showed a slow degradation rate, with an average kinetic constant of 0.008 d^-1. Products degradation was monitored by recovering samples from tests after 30, 60 and 90 days. After 30 days, all products showed changes in colour and fragmentation, that were more pronounced after 60 and 90 days. Degradation was also evident by the reduction of the carbonyl index and a decrease in the melting temperature. Nonetheless, differences in crystallinity, thermal properties, thickness and additives did not affect methane yield or degradation rate. Despite being fully biodegradable, biodegradation at full-scale was estimated at < 20 %, limiting the feasibility of anaerobic digestion as an end-of-life management option and highlighting the need for improved waste management strategies.