H2O2-aged biochar mediated co-composting of pig manure and rice bran efficiently removes antibiotic resistance genes by regulating microbial community and mobile genetic elements

Aged biochar remediation can effectively remove antibiotic resistance genes (ARGs) from cultivated soil. Nevertheless, the effect of aged biochar on the elimination of ARGs during aerobic composting remains unclear. This research conducted combined composting of pig manure with rice bran (NBC), along with the addition of fresh biochar (FBC) and H 2 O 2 -aged biochar (ABC), to assess the fates of 27 ARGs and 3 mobile genetic elements (MGEs). The total degradation rates of all 27 ARGs and 3 MGEs in ABC (68.5%) were significantly higher than those in FBC (55.7%) and NBC (15.7%). Over a 60-day composting period, 18 ARGs and 3 MGEs were degraded, while 9 ARGs became enriched. Network analysis and Mantel tests suggested that 18 degraded-ARGs are mainly regulated by MGEs. Notably, the higher pore size (PS), pore volume (PV), specific surface area (SSA) and oxygenated functional groups (OFG) in aged biochar contribute to a greater decline in MGEs, thereby fortifying the disposal of 18 degraded-ARGs. Additionally, according to the co-occurrence network, the enrichment of 9 ARGs is attributed to an increase in their potential host bacteria during the later stages of composting. Because of ecological competition, the relatively higher abundances of Thermomonas and Clostridium in ABC during these period reduced the abundances of potential host bacteria for the 9 enriched-ARGs. Therefore, significantly lower abundances of 9 enriched-ARGs were observed in ABC. Summarily, aging with H 2 O 2 fortified the capability for the removal of ARGs in biochar, which provides new insights for the reduction of ARGs in composting. • Composting led to the removal of 18 ARGs, but conduced to the enrichment in 9 ARGs. • Biochar addition reduced ARGs during composting, and aged biochar had greater effect. • Aged biochar addition removed degraded-ARGs by reducing MGEs during composting. • Aged biochar addition removed enriched-ARGs by restricting their host bacteria. • Bacteria in genera Thermomonas and Clostridium mainly inhibited enriched-ARGs.