Effect of a semi-permeable membrane covered composting on greenhouse gas emissions and bacterial community succession: A comparative study with biomass materials covering

This study investigated the effects of cornstalk, sawdust, and semi-permeable membrane covering on gaseous emissions and bacterial communities during composting, and the physicochemical and biodegradable characteristics of covered compost piles. The results showed that cornstalk covering increased NH3 emissions by 1.5% and reduced N2O emissions by 47.0%, and the sawdust covering synergistically reduced NH3 and N2O emissions by 42.1% and 23.2%, respectively. The biomass materials covering reduced gaseous emissions through physical adsorption and biotransformation. Total nitrogen (TN) emissions increased from 12.50 to 35.90 g kg(-1) for cornstalk and from 1.60 to 7.10 g kg(-1) for sawdust, while the nitrogen-reducing bacteria substantially increased from 0.21-0.28% to 1.98-2.44% in biomass covering materials. The biomass materials covering increased electrical conductivity and reduced the diversity and network complexity of bacterial communities in compost. Finally, the lignocellulosic structure and functional groups of the biomass materials were destroyed, thus biomass material could not be reused. Correspondingly, the membrane covering simultaneously decreased NH3 emissions by 53.9% and N2O emissions by 71.3%. In addition to physical interception, the nitrogen-reducing bacterial communities enriched on the membrane surface (Georgenia and Limnobacter) further reduced NH3 and N2O emissions. The bacterial communities in membrane-covered treatment exhibited concentrated connections and potential cooperation. As a result, the membrane covering achieved higher maturity and better reduction performance of gaseous emissions. Characterization of covering materials revealed that the membrane structure was intact and could be reused. Interestingly, after composting, the membrane surface formed a "microbe-rich biofilm", which exhibited better performance in subsequent covering processes.