Anaerobic co-digestion of HDPE plastics with fruit and vegetable waste: Insights into partial biodegradation and...

The global accumulation of HDPE waste poses significant environmental challenges due to its recalcitrant nature and resistance to degradation. Biological treatment methods, particularly anaerobic digestion, offer a sustainable alternative for mitigating plastic pollution while recovering energy in the form of biogas. This study investigates the co-digestion of HDPE plastics with fruit and vegetable waste using a two-stage anaerobic digestion system in batch mode. The process was evaluated for its potential to facilitate HDPE biodegradation while maintaining overall digester performance. Results showed that although methane production was affected by maximum 19.57 % decrease, the system exhibited stable operation without signs of inhibition. Notably, HDPE biodegradation was evidenced by mass losses of 14.02 % for pellets and 17.7 % for waste plastics. SEM analysis revealed surface morphological changes in the HDPE samples, while FTIR confirmed functional group modifications, supporting the observed degradation. Microbial community analysis via 16S rRNA sequencing identified Firmicutes, Bacteroidetes, and Proteobacteria as dominant phyla involved in the hydrolysis stage. A carbon mass balance analysis further elucidated carbon flow and transformation within the system. This study highlights the potential of anaerobic co-digestion as an integrated approach for partial HDPE biodegradation and organic waste valorization, paving the way for future optimization strategies.