Effect of fermentation materials reflux on gaseous emissions during perishable waste composting

Aiming at the problems of low bioconversion efficiency and serious secondary pollution of urban perishable waste (PW), fermentation materials reflux was applied in PW composting to investigate the effects of reflux modes on emission of ammonia (NH3), methane (CH4) and nitrous oxide (N2O) in this study. Before that, 20% was determined to be the optimal ratio of reflux in terms of the indicators of gaseous emissions and used in the current experiment. Five treatments including CK (no-reflux), T1 (reflux mature compost (MC), completely mixed with the initial material), T2 (reflux MC, 15% for initial mixing, 5% for surface covering), T3 (reflux MC, 10% for initial mixing, 10% for surface covering) and T4 (reflux thermophilic compost (TC) and MC, 15% TC for initial mixing, and 5% MC for surface covering). T2 reduced NH3 and CH4 emission by 52.9% and 40.11%, as a result of high temperature and inhibition of methanogens in the former stage. While T4 reduced the most N2O emission by 56.85% through the restraint of denitrification. In conclusion, the introduction of fermentation materials can accelerate the composting process, improve maturity, and mitigate greenhouse gas (GHG) emissions ranging from 27.61% to 58.05%, which can provide theoretical and technical support for rapid composting of urban PW in the future.