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Effects of functional membrane coverings on carbon and nitrogen evolution during aerobic composting: Insight into the succession of bacterial and fungal communities

Functional membrane-covered aerobic composting; Carbon forms; Nitrogen forms; Greenhouse gases; Microbial community structure.

Aerobic composting is a simple, economical, and environmentally benign technique that is widely used to treat agricultural waste. Aerobic composting causes emissions of carbonaceous gases (carbon dioxide (CO₂) and methane (CH₄)) and nitrogenous gases (ammonia (NH₃) and nitrous oxide (N₂O)), resulting in carbon and nitrogen being lost and the organic fertilizer produced being less effective. Functional membrane-covered aerobic composting (FMCAC) is widely used to treat various types of organic waste because smaller amounts of greenhouse gases and odorous compounds are emitted during FMCAC than during conventional composting. The functional membrane contains a polytetrafluoroethylene film functional layer sandwiched between two polyurethane layers. Different manufacturing techniques are used by different manufacturers, so different functional membranes have different pore size and air permeabilities, which ultimately affects the formation of micro-positive pressure and the fermentation during aerobic composting. Therefore, it is necessary to explore the effect of functional membrane properties on carbon and nitrogen emissions. Carbon and nitrogen evolution and bacteria and fungi succession in two functional membrane-covered aerobic composting (FMCAC) systems and a conventional aerobic composting system were investigated. The micro-positive pressure in each FMCAC system altered the composting microenvironment, significantly increased the oxygen uptake rates of microbes (P<0.05), and increased the abundance of cellulose- and hemicellulose-degrading microorganisms. Bacteria and fungi together influenced the conversion between carbon and nitrogen forms. FMCAC made the systems less anaerobic and decreased CH₄ production and emissions by 22.16%–23.37% and N₂O production and emissions by 41.34%–45.37% but increased organic matter degradation and NH₃ production and emissions by 16.91%–90.13%. FMCAC decreased carbon losses, nitrogen losses, and the global warming potential by 7.97%–11.24%, 15.43%–34.00%, and 39.45%–42.16%, respectively. The functional membrane properties (pore size distribution and air permeability) affected fermentation process and gaseous emissions. A comprehensive assessment indicated that FMCAC has excellent prospects for application.