Anaerobic Biodegradation of Bioplastic Packaging Materials

Abstract

With multiple initiatives to keep food-waste away from landfills, packaging systems that are compatible with the alternative end of life scenario (e.g., composting, biodigestion) are required. Anaerobic digestion converts biodegradable materials into energy-rich biogas. However, currently, the plastic packaging for handling food scraps have to be separated before digestion even if the plastic is regarded as biodegradable because they do not degrade in the required timeframe. If the biodegradation rate of bioplastics can match that of organic waste, the foodwaste and packaging can be comingled in a single stream. Polymers such as polylactic acid (PLA), polycaprolactone (PCL) and polybutylene succinate (PBS) have a diverse range of applications. However they take a prolonged period to degrade completely. On the contrary, thermoplastic starch and polyhydroxyalcanoate (PHA) stand out as fast degrading polymers that can be compounded into polylactic acid to improve biodegradation. This study investigated the anaerobic biodegradation of commercially available bioplastics and potential ways to increase biodegradation rates. Commercial polymers were melt blended and converted into films including PLA and PLA blends with PCL and PBS. The effect of calcium carbonate as an additive was also evaluated. A laboratory scale automated methane potential testing system was used to study the degradation behavior. Calcium carbonate at low concentrations showed potential to improve biodegradation rates by providing a pathway for microbial activity. Co-digestion of PLA with food-waste resulted in a 10% increase in biomethane potential, indicating a synergistic effect. The results showed the potential for developing packaging solutions for handling food-waste that can readily degrade in industrial anaerobic digestion facilities.