Effects of biochar and volcanic rock addition on humification and microbial community during aerobic composting of cow manure

Additives are important for accelerating humification during aerobic composting. The impacts of porous additives biochar and volcanic rock on the physicochemical parameters, maturity indicators, microbial communities, and bacterial functional metabolism during the aerobic composting of cow manure were investigated in this study. The results showed that the biochar addition decreased the E4/E6 value by 10.42% and increased the abundance of Geobacillus (1.69 times), and volcanic rock addition decreased the E4/E6 value by 11.31% and increased the abundance of Thermobacillus (1.29 times) and Paenibacillus (1.72 times). The network analysis demonstrated that biochar promoted maturity by reducing the abundance of Pseudomonas and increasing the abundance of genes related to the metabolism of other amino acids, while volcanic rock promoted maturity by reducing the abundance of genes related to nucleotide metabolism. These results provided data and theoretical justification for the selection of porous additives for composting.