Unravelling biotic and abiotic mechanisms of mature compost to alleviate gaseous emissions in kitchen waste composting by metagenomic analysis.

Mature compost can reduce gaseous emissions in composting, but its regulation mechanisms via biotic and abiotic functions are largely unknown. This study used fresh and inactivated mature compost as additives in kitchen waste composting to unveil the relevant mechanisms using metagenomic analysis. Results showed that mature compost reduce gaseous emission by improving physiochemical properties and inoculating functional microbes. The abiotic function of mature compost alleviated methane and nitrous oxide emission by 20 % via enhancing air diffusion and pH to limit the activity of mcr, mtr, norB/C, and narG/H hosts. Compared to inactivated mature compost, the microbes in fresh counterpart promoted organic mineralization to slightly enhance ammonia release by 9 %, but alleviated 13 % of carbon dioxide emission through microbial humification to impel carbon sequestration. Therefore, another specialistic strategy (e.g. Calcium magnesium phosphate addition to form struvite Crystallization) should be integrated with mature compost to synergistically reduce gaseous emissions.