Exploring the impact of biochar on antibiotics and antibiotics resistance genes in pig manure aerobic composting through untargeted metabolomics and metagenomics

[Display omitted] •Biochar can promote the degradation process of TCs during aerobic composting.•ARGs were transferred from Firmicutes to Actinobacteria at the phylum level.•The RA of ARGs in the biochar group was reduced by 16.83 ± 4.10%.•Biochar facilitates the removal of sav1866, ImrD, efrA, tetB(P), and tetL. This study investigated the effect of biochar on antibiotics and antibiotic resistance genes (ARGs) during aerobic composting of pig manure. First, the composition and content of antibiotics in the manure were determined qualitatively and quantitatively. Biochar promoted the degradation of these antibiotics (oxytetracycline, chlortetracycline, and tetracycline). The relative abundance (RA) of antibiotic-resistant bacteria carrying ARGs accounted for about 29.32% of the total bacteria. Firmicutes and Actinomycetes were dominant phylum-level bacteria at the early and late stages of composting, respectively. Biochar decreased the total RA of ARGs by 16.83%±4.10%. tetW and tetL, closely related to tetracycline resistance, were significantly diminished during aerobic composting, and biochar was able to promote this removal. Biochar enhanced RAs of Mycobacterium tuberculosis kasA mutant. RAs of ARGs related to antibiotic efflux pumps, such as baeS and arlS, remained at a high level. Conclusively, biochar promotes degradation of antibiotics and removal of ARGs.