Evaluations of biochar amendment on anaerobic co-digestion of pig manure and sewage sludge: waste-to-methane conversion, microbial community, and antibiotic resistance genes.

Effects of biochar on co-digestion of pig manure and dewatered sewage sludge under different total solids (TS) were investigated. Biochar could accelerate the start-up of methanogenesis and shorten the adaptation phase. At TS5%, the methane daily production in biochar group was 60.6% higher than the control; nevertheless, when TS increased, the gap between two groups gradually narrowed. Additionally, the change on antibiotics resistance genes (ARGs) was also affected by TS and the biochar addition. Moreover, biochar was beneficial to reduce ARGs in liquid phase. At TS14%, the total ARGs abundance in the liquid phase of biochar group was 41.4% lower than the control, among which the reduction rates of etB(P), sul1, rpoB2, macA, mupA and mupB were more prominent. These findings could provide useful guidance for developing ARGs elimination strategy before their release into the environment.