Effect of spent mushroom substrate as a bulking agent on gaseous emissions and compost quality during pig manure composting.

The aim of this study was to investigate the gaseous emissions (CH4, N2O, and NH3) and compost quality during the pig manure composting by adding spent mushroom substrate (SMS) as a bulking agent. The control treatment was also studied using corn stalk (CS) as a bulking agent. The experiment was conducted in a pilot scale composting reactor under aerobic condition with the initial C/N ratio of 20. Results showed that bulking agents significantly affected gaseous emissions and compost quality. Using SMS as a bulking agent improved composting efficiency by shortening the time for maturity. SMS increased germination index and humic acid of the final compost (by 13.44 and 41.94%, respectively) compared with CS. Furthermore, composting with SMS as a bulking agent could reduce nitrogen loss, NH3, and N2O emissions (by 13.57, 35.56, and 46.48%, respectively) compared with the control. SMS slightly increased CH4 emission about 1.1 times of the CS. However, a 33.95% decrease in the global warming potential of CH4 and N2O was obtained by adding SMS treatment. These results indicate that SMS is a favorable bulking agent for reducing gaseous emissions and increasing compost quality.