Changes of carbon and nitrogen gas emissions and pathogenic bacteria during membrane-covered manure residue fermentation for bedding material production in a large dairy farm

The dairy manure residue is majorly used for producing bedding material by aerobic fermentation, but high-temperature fermentation causes large amounts of carbon and nitrogen gas emissions, which need to be urgently reduced and controlled. In this study, three 230 m³ treatment piles including the non-covered group (CK), the membrane-covered group (CV), and the membrane-covered manure residue mixed with rice husk group (CV+RH) were set up in a large-scale dairy farm, aiming to investigate the effects of different treatments on gas emissions and pathogenic bacteria killing effects over a 12-day fermentation period. The results showed that the cumulative emissions of NH₃ were 23.4, 1.0 and 0.2 g·m^-2 in CK, CV, and CV+RH, respectively, 10.5, 6.0 and 7.7 kg·m^-2 for CO₂, 52.6, 33.3 and 42.1 g·m^-2 for CH₄, and 93.1, 68.3 and 38.6 mg·m^-2 for N₂O. Compared to CK group, the cumulative emissions of NH₃, CO₂, CH₄, N₂O, GHG were reduced by 95.7%, 42.9%, 36.7%, 26.6% and 36.5% in CV group. The CV+RH group further enhanced the emission reduction effects for NH₃ and N₂O by 80.0% and 43.5%, respectively, when compared to CV. However, it increased CH₄ and CO₂ emissions and resulted in additional cost. Salmonella and Staphylococcus aureus were undetectable in all treatments throughout the experimental period. The high-temperature phase of manure residue fermentation achieved effective inactivation of E. coli in all groups. However, the maximum temperature of the CV+RH pile consistently remained below 70℃, which had a minor impact on mold inactivation efficiency. It was shown that covering with a functional membrane effectively controlled greenhouse gases and ammonia emissions during fermentation process. However, the addition of rice husk did not significantly enhance the reduction of overall GHG emissions. Bedding materials produced by both techniques met the pathogen-related criteria specified in bedding standards. The technology of using membrane-covered manure residue fermentation for bedding material production can effectively reduce the gas pollution and provide safe and comfortable bedding material for dairy farms.