Abstract:
Aerobic fermentation of dairy manure residue for bedding regeneration is a key manure treatment model in dairy farms, while high-temperature fermentation causes large amounts of carbon and nitrogen gas emissions, which need to be urgently reduced and controlled. An in-situ experiment was conducted at a large-scale dairy farm to evaluate the effects of membrane-covered fermentation of dairy manure residue on gas emissions and pathogen inactivation during the bedding material production process. The experiment was carried out with three treatments: cattle manure residue + uncovered fermentation (CK), cattle manure residue + membrane-covered fermentation (CV), and cattle manure residue and rice husk + membrane-covered fermentation (CV+RH). Each pile had a volume of 230 m
3. A forced aeration strategy was employed with a 25-min turn-on and 35-min turn-off regimen, delivering an average ventilation rate of 0.30 m
3/(min·m
3 pile). The results showed that the time with pile temperature higher than 55 ℃ kept for more than nine days in each treatment, meeting the requirements for the thermophilic phase in bedding material fermentation. CK, CV, and CV+RH treatments showed the cumulative NH
3 emissions of 23.4, 1.0, and 0.2 g/m
2, cumulative CO
2 emissions of 10.48, 6.01, and 7.65 kg/m
2, cumulative CH
4 emissions of 52.6, 33.3, and 42.1 g/m
2, and cumulative N
2O emissions of 93.1, 68.3, and 38.6 mg/m
2, respectively. Compared with CK treatment, CV treatment showed reductions of 95.7%, 42.7%, 36.7%, 26.6%, and 36.6% in the cumulative emissions of NH
3, CO
2, CH
4, N
2O, and total greenhouse gases (GHG), respectively. CV+RH treatment further enhanced the emission reduction effects of CV treatment, reducing the cumulative emissions of NH
3 and N
2O by 80.0% and 43.5%, respectively, compared with CV treatment. However, it increased cumulative CH
4 and CO
2 emissions.
Salmonella and
Staphylococcus aureus were undetectable in all treatments throughout the experimental period. The high-temperature phase of the manure residue fermentation process achieved effective inactivation of
Escherichia coli in all treatments. However, the maximum temperature of the CV+RH pile did not reach 70 ℃, which had a minor impact on the mold inactivation. Manure fermentation covered with a functional membrane effectively controlled GHG and NH
3 emissions during the fermentation process. However, the addition of rice husk could not enhance the reduction of overall GHG emissions significantly. Bedding materials produced by all treatments met the pathogen-related criteria specified in bedding material standards. Membrane-covered fermentation of cattle manure residue is recommended for bedding material production, which can effectively reduce gas pollution and provide safe and comfortable bedding material for dairy farms.