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Biodegradation of poly(butylene succinate) in soil laboratory incubations assessed by stable carbon isotope labelling
Summary
Researchers used carbon isotope labeling to precisely track how biodegradable plastic (poly(butylene succinate)) breaks down in agricultural soil over more than a year, finding that 65% fully converted to CO2 while the rest integrated into the soil. This new tracking method provides a reliable way to evaluate whether "biodegradable" plastics actually decompose as claimed in real soil conditions.
Using biodegradable instead of conventional plastics in agricultural applications promises to help overcome plastic pollution of agricultural soils. However, analytical limitations impede our understanding of plastic biodegradation in soils. Utilizing stable carbon isotope (13C-)labelled poly(butylene succinate) (PBS), a synthetic polyester, we herein present an analytical approach to continuously quantify PBS mineralization to 13CO2 during soil incubations and, thereafter, to determine non-mineralized PBS-derived 13C remaining in the soil. We demonstrate extensive PBS mineralization (65 % of added 13C) and a closed mass balance on PBS-13C over 425 days of incubation. Extraction of residual PBS from soils combined with kinetic modeling of the biodegradation data and results from monomer (i.e., butanediol and succinate) mineralization experiments suggest that PBS hydrolytic breakdown controlled the overall PBS biodegradation rate. Beyond PBS biodegradation in soil, the presented methodology is broadly applicable to investigate biodegradation of other biodegradable polymers in various receiving environments.