Mimicking real-field degradation of biodegradable plastics in soil and marine environments: From product utility to end-of-life analysis

Abstract

Biodegradable plastics can mitigate plastic waste issues by undergoing hydrolysis and microbial digestion. However, biodegradable plastics face unjust accusations of not decomposing in natural environments, including barren soil or cold oceans, under unsuitable conditions. In this study, we simulated end-of-life of biodegradable plastic products under real-field soil and seawater conditions. Replenishing vermicompost in horticultural topsoil (3:7 wt ratio) activated microbial growth, resulting in significant degradation. In fertile soil, polycaprolactone (PCL) and poly(butylene succinate) (PBS) required fewer than 6-months, for complete degradation, while poly(butylene adipate-co-terephthalate) (PBAT) with more than 51 mol% terephthalate content was rarely degraded. In an artificial seawater aquarium, PCL degraded at the rate of 30 μm per month. The degradation of bioplastics enclosed in coarse nets was superior to that in fine nets, owing to higher aeration and water circulation. Sea waves and current significantly accelerated the rate of PCL-degradation to 89 μm per month in a coastal marine environment; the ranking of rate of decomposition was PCL > PBS > PBAT. After 12 months of biodegradation, the tensile strength and elongation of a 2 mm-thick sample of PCL decreased to 15 MPa and almost 0 %, respectively. 3D-printed jars, designed for octopus fishing, is widely used and its designed mechanical decay aids in preventing the ghost fishing of abandoned gear as demonstrated by artificial conches, illustrating the potential for biodegradable fishing gear.