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-co-terephthalate (PBAT) and polybutylene sebacate-co-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.