Biodegradable plastics in anaerobic digestion environment

Sammanfattning

The increasing presence and use of bioplastics (BPs) as alternatives to conventional fossil-based plastics has raised concerns regarding their end-of-life (EoL) management and degradation behavior under anaerobic digestion (AD) conditions. Hence, this study evaluated the biodegradability of poly(lactic acid) (PLA), poly(butylene adipate-co-terephthalate) (PBAT), and their blends under thermophilic AD conditions using a manual manometric biochemical methane potential (BMP) assay. Biogas composition and volatile fatty acid (VFA) concentrations were monitored throughout the experiment and at intervals of 32 and 67 days respectively, while biodegradation kinetics were described using the modified Gompertz model and biodegradability was assessed on the basis of methane production and mass loss. Although PLA films demonstrated substantial and promising biodegradation under thermophilic AD conditions, none of the investigated materials achieved complete biodegradation within an incubation period of 32 days, representative of many full scale OFMSW digestion facilities. These findings suggest that retention times commonly employed in industrial AD systems may be insufficient for complete degradation of PLA and PBAT based materials. Since the overall process of AD involves complex interplay between several steps, future work incorporating microbial community sequencing and stable isotope tracing could provide deeper insights into biodegradation pathways and the microbial communities involved.