Effects of selenate on greenhouse gas release and microbial community variations during swine manure composting

Co-composting of livestock manure and selenate is an effective means to produce selenium-rich organic fertilizer. However the effect of selenate on greenhouse gas emission during composting is still unknown. To probe the influences of selenate on greenhouse gas and microbial community changes during swine manure composting. Various dose of selenate were added to the fresh swine manure and wheat straw for 80 days aerobic composting, sequentially labeled as T1 (control) to T6 (0, 1, 2, 3, 4 and 5 mg kg^-1). Results indicated that selenate generally increased the nitrous oxide (N₂O) and ammonia (NH₃) emissions while presented varying impacts on methane (CH₄) emissions. Compared with the control, adding 2 and 5 mg kg^-1 selenate reduced the CH₄ emission by 39.60% and 13.75%, respectively, while other concentrations presented opposite results. Meanwhile, adding 2 mg kg^-1 selenate could reduce the global warming potential and improve the compost maturity. According to the microbial results, adding 2 mg kg^-1 selenate enhanced the richness and variety of the microbes and might influence Proteobacteria, Chloroflexi, Actinobacteria and Methylococcaceae_unclassified to decrease the global warming potential.