Biodegradation of Synthetic Aliphatic-Aromatic Polyesters in Soils: Linking Chemical Structure to Biodegradability

Biodegradable aliphatic-aromatic copolyesters are commercially important and used in diverse applications, including soil-biodegradable mulch films. This work investigates the effects of copolyester chemical structure on soil biodegradability using ¹³C-labeled variants of polybutylene adipate-<i>co</i>-terephthalate (PBAT) and polybutylene sebacate-<i>co</i>-terephthalate (PBSeT), as well as ¹³C-labeled cellulose as a positive biodegradation control. Biodegradation in soil was assessed by monitoring polyester and cellulose mineralization to ¹³CO₂ throughout multimonth incubations and quantifying the nonmineralized polyester in the soil after incubations. Mass balances on polyester- and cellulose-added ¹³C over the incubations were closed. The soil biodegradability of PBSeT was higher than that of PBAT for variants with a molar ratio of terephthalate (T) to total diacid of 50%. PBAT biodegradability substantially increased as its T content decreased from 50% to 47, 30, 20, and 0%. Increasing biodegradability with decreasing T content also resulted in preferential biodegradation of aliphatic-rich domains in the initial phase of the incubations. Polyesters undergoing extensive mineralization also showed substantial incorporation of polyester carbon into the soil microbial biomass. Differences in polyester soil biodegradability were rationalized based on differences in their enzymatic hydrolyzability. Qualitative chemical structure-biodegradability relationships can lead to tailoring polyester biodegradability to specific applications and the biodegradation potentials of receiving environments.