Understanding the biodegradation of PHBV/Cellulose composites in mesophilic anaerobic digestion

Biodegradable plastics have been developed as alternative materials to prevent the environmental damage of conventional plastics on ecosystems. However, their end of life depends on environmental conditions in which they are disposed of. Their management in anaerobic digestion (AD) remains a topic of debate and needs further investigation. This study assesses the behaviour of PHBV, a prominent bio-based biodegradable plastic, blended with cellulose fibres in mesophilic AD conditions. Results show that degradation depends on material characteristics such as its specific surface area and cellulose content. Nearly complete biodegradation is observed for 1 mm diameter powder and 67 % degradation for 2 × 2 cm films over 57 days of AD at 38 °C. Biodegradation is faster with higher cellulose content up to 40 %. Morphological, structural, and functional analyses indicate that biodegradation occurs primarily through surface erosion, resulting in reduced polymers molecular weight and crystallinity, along with shifts in functional ester groups. Specific microbial genera, such as Ruminofilibacter , Thiospeudomonas , and HN.HF0106 , were abundant in the planktonic phase, while Ruminofilibacter , Clostridium sensu stricto 7 , UCG.012 , and Treponema dominated the biofilm during AD. This research aims to provide deeper understanding of PHBV degradation mechanisms in AD, crucial for effective management in such conditions. • PHBV materials show high degradation in mesophilic anaerobic digestion in 60 days. • PHBV/Cellulose composites with higher cellulose content degrade faster. • Material analysis reveals surface degradation mechanism. • Biofilm attached to the materials is enriched in Clostridium and Ruminofilibacter .