Hydrothermal carbonization: A potent strategy for simultaneously eliminating ARGs-associated pollutants in livestock...

Antibiotic resistance is a major One Health concern, with livestock manure being a key source of antibiotics, antibiotic resistance genes (ARGs), and pathogens. While conventional treatments such as composting and anaerobic digestion often show incomplete removal and potential ARGs enrichment, hydrothermal carbonization (HTC) offers a promising alternative solution for managing high-moisture swine manure. The effectiveness of HTC was systematically evaluated under varying temperatures (100-240 °C), reaction times (30-240 min), and solid-liquid ratios (1:4-1:8) in this study. Results demonstrated that HTC at 220-240 °C for ≥ 90 min could completely eliminate ARGs and mobile genetic elements (MGEs) from raw pig manure (initial abundance: 10⁸-10 ¹⁵ copies/16S rRNA gene), and achieve complete degradation of target antibiotics and pathogens. Furthermore, hydrochar suspensions reduced plasmid RP4 conjugative transfer by 85-98 %, primarily by lowering bioavailable Cu^2 + /Zn²⁺ levels, thus inhibiting horizontal gene transfer. Hydrochar at 240 °C outperformed 220 °C, with 52.2-66.4 % lower bioavailable metal concentrations. These findings establish HTC as an efficient strategy for mitigating ARGs spread and enabling safe manure reuse, with advantages in both treatment efficacy and economic viability over conventional methods.