Fate of a biobased polymer via high-solid anaerobic co-digestion with food waste and following aerobic treatment: Insights on changes of polymer physicochemical properties and the role of microbial and fungal communities

• A PBAT/PLA blend is tested for anaerobic co-digestion with high-solid contents. • No biogas improvement is achieved after a long residential time of AD. • Food waste co-digestion greatly deteriorates the polymer hydrophobicity. • Polymer after 55℃ AD shows better biodegradability in aerobic post-treatment. • Polymer cracking at 55℃ may form microplastics and deteriorate digestate quality. Degradation of bioplastics in food-waste-treating anaerobic digestion (AD) plants is becoming an increasingly concerning issue as they are inevitably mixed with food waste during the waste collection process. The aim of this study was to assess the degradation of PBAT/PLA based biopolymer bags during mesophilic and thermophilic AD, co-digested with food waste, and subsequent aerobic post-treatment. After the AD process, no discernable biological degradation was observed for all of the PBAT/PLA polymers. The comparison of FTIR, XRD, TG analysis and contact angle analysis between raw and degraded PBAT/PLA polymer revealed structural changes after anaerobic incubation. Subsequent aerobic treatment facilitated the degradation of the PBAT/PLA polymers from thermophilic AD, which was attributed to the polymer-degrading microorganisms Brevundimonas and Sphingobacterium . Physical disintegration of the PBAT/PLA polymer was observed under thermophilic conditions. Those undegraded polymer fragments could affect digestate quality and increase the risk of releasing microplastics into the environment.