Semi-Permeable Membrane Covering Reduces Gaseous Emissions and Promotes Mineral-N Retention During Swine Manure Composting

Nitrogen loss during manure composting reduces the fertilizer value of the final product and increases its environmental burden. This study evaluated whether semi-permeable membrane covering could reduce gaseous emissions and promote mineral-N retention during the co-composting of swine manure and spent mushroom substrate. Conventional aerobic composting (AC) and semi-permeable membrane-covered aerobic composting (MCAC) were conducted for 35 d. Compared with AC, MCAC reduced the estimated cumulative emissions of NH3, N2O, and CH4 by 53.1%, 34.1%, and 45.7%, respectively, and lowered the estimated direct global warming potential of direct CH4 and N2O emissions by 37.5%. On day 35, MCAC had higher NH4+-N (530.5 vs. 172.0 mg kg−1) and NO3−-N concentrations (80.1 vs. 42.6 mg kg−1) than AC. Total nitrogen concentration decreased by 14.98% in MCAC and 17.82% in AC from day 1 to day 35. Composting stage explained 33.95% of bacterial community variation, versus 5.71% for membrane covering. Metagenomic nitrogen-cycling profiles varied mainly over time, with higher ammonia-oxidation potential in MCAC on day 10. Profiles covaried mainly with moisture and inorganic nitrogen. Overall, semi-permeable membrane covering maintained thermophilic composting while reducing gaseous emissions. The lower NH3 and N2O emissions, together with the higher final NH4+-N and NO3−-N concentrations, indicate reduced gaseous N release and greater mineral-N retention under MCAC.