Exploring the mechanisms of decreased methane during pig manure and wheat straw aerobic composting covered with a semi-permeable membrane.

It is very important to reduce methane production and emission during aerobic composting. In this study, the effects of covering with a semi-permeable membrane during pig manure and wheat straw composting were investigated. Two laboratory-scale composting reactors were used: the membrane covered treatment (treatment A) and the control treatment (treatment B). Composting in treatment A effectively improved the oxygen utilization rate and decreased methane emissions by 22.42% relative to the control treatment. Quantification of functional genes and Pearson rank correlations showed that the mcrA and mcrA/pmoA gene abundances were significantly positively correlated with temperature and negatively correlated with the interstitial oxygen concentration, and that the pmoA gene abundance was positively correlated with the carbon: nitrogen ratio and moisture content. Therefore, increasing the aeration rate and optimizing the carbon: nitrogen ratio and moisture content will decrease methane emissions. Together, the results demonstrate that coverage membrane could be a novel strategy for reducing methane emissions during composting.