Technological watch

This review examines cradle-to-grave life cycle assessments (LCAs) and biodegradation studies of common bioplastics. Fueled by a growing single-use consumer base, the rate at which plastics are produced and disposed of is outpacing most other man-made materials, which is leading to substantial environmental impacts. Plastics from bio-based feedstocks (i.e., bioplastics) are a commonly discussed option to help mitigate impacts of petroleum-based plastic production. However, there is still a limited understanding of the best practices for waste management of these plastics. Here we review the end-of-life (EoL) assumptions for bioplastic LCA studies and compare these to experimental findings to identify research gaps and highlight sources of uncertainty. The majority of existing LCA literature, including 17 out of 22 studies reviewed herein, focus on the environmental impacts from three key bioplastics: polylactic acid, polyhydroxyalkanoates, and thermoplastic starch. However, these bioplastics are projected to account for only 29% of the future plastic consumption based on their current technical feasibility. Further, within these LCA studies, there remain limited modeling efforts for anaerobic digestion as an EoL option; yet, this is one of the predominant disposal pathways studied in the experimental literature. Due to limited data for the behavior of bioplastics at EoL, LCA studies contain assumptions that lead to high levels of variability and uncertainty in environmental impact results, with many modeling assumptions and by-product applications differing significantly from the current waste management system. Findings of this review also highlight areas of future research, such as mechanisms to leverage the potential circularity of these bioplastics.