Two-phase removal kinetics of antimicrobial resistance in collaborative composting: Thermophilic enhancement and...

Temperature significantly affects antimicrobial resistance (AMR) during composting, but its role in multi-material co-composting remains unclear. This study explored temperature effects on pathogen inactivation, antibiotic resistance gene (ARG) removal, and host dynamics. Three composting regimes were established based on temperature: thermophilic (TC, <65 °C), superthermophilic (SC, 65-75 °C), and hyperthermophilic (HC, >75 °C). Fecal coliforms were inactivated within 2 days at > 65 °C, compared to 3 days at 40-50 °C. Temperatures exceeding 65 °C accelerated pathogen elimination, achieving over 98% reduction by day 28. During the thermophilic phase, elevated temperatures (>65 °C) suppressed vertical gene transfer and removed 95%-97% of ARGs by day 28. In the maturation phase, maintaining moisture content (MC) below 40% mitigated ARG rebound by restricting horizontal gene transfer, bacterial activity, and mobile genetic elements (MGEs). Six high-risk ARGs (tetW, aadE, ermX, ermB, sul1, tetM) and their pathogenic hosts (Enterococcus, Escherichia, Streptococcus, Clostridium, Corynebacterium) were identified. By day 28, treatments exceeding 65 °C eliminated 96%-99% of pathogens, high-risk ARGs, and their hosts, with no ARGs rebound detected in the final compost. Overall, maintaining composting temperatures above 65 °C for at least five consecutive days and controlling final MC below 40% constitutes an effective strategy for mitigating AMR risks in multi-material co-composting. This study provides both theoretical and technical foundations for managing antibiotic resistance risks during composting.