Zero-valent iron accelerates biodegradable plastic fragments (BPFs) aging during aerobic composting: Insights from...

Composting is an environmentally sustainable approach to organic waste treatment. However, biodegradable plastic fragments (BPFs) are constantly entering solid waste streams due to improper disposal and affecting the composting system, in which BPFs inevitably undergo aging. Zero-valent iron (ZVI) is commonly utilized as a conditioning agent to enhance composting efficiency and product quality, driven by the microbial process. Nevertheless, the impact of ZVI on the aging mechanisms of BPFs within the composting system remains an unexplored area. To address this knowledge gap, we conducted an aerobic compost to investigate the aging mechanisms of BPFs in the ZVI-conditioned composting system. The results demonstrated that BPFs exhibited more significant aging characteristics in the ZVI-conditioned composting system, including notable chromatic alterations (16.01 %-36.33 %), substantial mass degradation (8.62 %-57.45 %), and enhanced biofilm formation (7.41 %-174.10 %). Mechanistically, the addition of ZVI not only alleviated the environmental constraints on microbial communities, but also promoted a restructuring of the community that may enrich specific bacterial taxa with potential plastic-degrading capacities, thus accelerating the degradation. The results provide valuable insights into the aging process of BPFs in the ZVI-conditioned composting system and the innovative strategies for mitigating plastic pollution through the utilization of ZVI conditioning agents.