Biodegradable Plastic Blends Create New Possibilities for End-of-Life Management of Plastics but They Are Not a Panacea for Plastic Pollution

TLDR

Plastic waste pollution is a global problem that biodegradable plastics could help mitigate, yet the environmental fate of blended biodegradable polymers, including PLA, remains largely unknown. We tested neat polymers (PLA, PHB, PHO, PBS, thermoplastic starch, PCL) and their blends for biodegradation across seven managed and unmanaged environments. PLA blended with PCL becomes home‑compostable, most tested bioplastics and blends degrade in thermophilic anaerobic digestion with high biogas output but 3–6 times longer than commercial plant retention, while many fail ISO/ASTM standards, underscoring the need for careful post‑consumer management and faster‑degrading designs.

Abstract

Plastic waste pollution is a global environmental problem which could be addressed by biodegradable plastics. The latter are blended together to achieve commercially functional properties, but the environmental fate of these blends is unknown. We have tested neat polymers, polylactic acid (PLA), polyhydroxybutyrate, polyhydroxyoctanoate, poly(butylene succinate), thermoplastic starch, polycaprolactone (PCL), and blends thereof for biodegradation across seven managed and unmanaged environments. PLA is one of the world's best-selling biodegradable plastics, but it is not home compostable. We show here that PLA when blended with PCL becomes home compostable. We also demonstrate that the majority of the tested bioplastics and their blends degrade by thermophilic anaerobic digestion with high biogas output, but degradation times are 3-6 times longer than the retention times in commercial plants. While some polymers and their blends showed good biodegradation in soil and water, the majority of polymers and their blends tested in this study failed to achieve ISO and ASTM biodegradation standards, and some failed to show any biodegradation. Thus, biodegradable plastic blends need careful postconsumer management, and further design to allow more rapid biodegradation in multiple environments is needed as their release into the environment can cause plastic pollution.