Biochar Addition Modified Carbon Flux and Related Microbiota in Cow Manure Composting

Carbon emission is the main cause of carbon loss during composting. This study investigated the effect of bamboo biochar addition to compost on carbon dioxide (CO2) release and fixation through metagenomics sequencing. The results showed that the addition of biochar enriched the relative abundance of ribulose-1,5-diphosphate carboxylase/oxygenase (RuBisCO) gene by 13.22%, improving the diversity of carbon-fixing microbiota. In addition, biochar also inhibited the relative abundances of pyruvate dehydrogenase (PDH), isocitrate dehydrogenase (IDH), and alpha-ketoglutarate dehydrogenase (A_KGD) at the late stage of composting, thereby reducing the CO2 release by 16.77%. Bamboo biochar also decreased the abundance of Methyl coenzyme-M reductase (MCR), which in turn reduced methane (CH4) release. Redundancy analysis (RDA) showed that Proteobacteria was the dominant phylum in the compost system during the cooling and maturity periods, which dominated the release of CO2 and was positively correlated with PDH, IDH, and A_KGD (p < 0.01). In addition, RubisCO was negatively correlated with organic matter (OM), CO2, CH4 (p < 0.01). Taken together, biochar can inhibit the activity of CO2-releasing microorganisms, thereby reducing carbon loss in composting. [GRAPHICS] .