Effects of biochar addition and semi-permeable membrane covering on aerobic composting: Insights into carbon–nitrogen transformations and bacterial community and function succession

This study investigated carbon and nitrogen transformations, as well as patterns in bacterial community structures and metabolic functions, during membrane-covered aerobic composting (MCAC), biochar-amended aerobic composting (BAAC), and conventional aerobic composting. Both MCAC and BAAC improved the composting aerobic environment, increased the abundance of organic matter-degrading bacteria and methane-oxidizing norank_f__Methylococcaceae , and downregulated the abundance of denitrifying bacteria and functional modules associated with methane generation and denitrification, thereby affecting carbon and nitrogen transformations. Compared with conventional composting, BAAC reduced cumulative CH 4 , N 2 O, and NH 3 emissions by 29%, 16%, and 21%, respectively, while MCAC reduced cumulative CO 2 , CH 4 , and N 2 O emissions by 2%, 6%, and 68%, respectively. Under both treatments, nitrogen losses and global warming potential declined by 44%–50% and 16%–67%, respectively, alongside increases of 8%–10% in sanitization and 3%–4% in humification. Overall, BAAC was more effective in mitigating CH 4 and NH 3 emissions, whereas MCAC achieved remarkable N 2 O mitigation and offered lower implementation costs. These complementary strengths suggest that each approach holds considerable potential for practical application, and that integrating the two may further optimize composting performance while balancing environmental and economic outcomes. • Biochar addition (BC) and membrane covering (MC) reduced nitrogen losses by 44%–50%. • BC and MC improved bacterial community composition and metabolic functional modules. • BC reduced cumulative CH 4 , N 2 O, and NH 3 emissions by 29%, 16% and 21%, respectively. • MC reduced cumulative CO 2 , CH 4 , and N 2 O emissions by 2%, 6% and 68%, respectively. • BC and MC enhanced sanitization and humification during aerobic composting.