Abstract:
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. An in-situ experiment was conducted at a large-scale dairy farm to evaluate the effect of membrane-covered fermentation of dairy manure residue on gaseous emissions and pathogen inactivation during the bedding material production process. Three treatment piles were set in this experiment: an uncovered control group (CK), a membrane-covered group (CV), and a pile of manure residue mixed with rice husk and being membrane-covered (CV+RH). Each pile had a volume of 230 m
3. A forced aeration strategy was employed with an interval of 25 minutes turn-on and 35 minutes 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 fermentation. The cumulative emissions of NH
3 were 23.4, 1.0 and 0.2 g/m
2 in CK, CV, and CV+RH, respectively, 10.48, 6.01and 7.65 kg/m
2 for CO
2, 52.6, 33.3 and 42.1 g/m
2 for CH
4, and 93.1, 68.3 and 38.6 mg/m
2 for N
2O. Compared with CK treatment, the cumulative emissions of NH
3, CO
2, CH
4, N
2O, and total GHG were reduced by 95.7%, 42.7%, 36.7%, 26.6% and 36.6% under CV treatment, respectively. The CV+RH treatment further enhanced the emission reduction effects of NH
3 and N
2O by 80.0% and 43.5%, respectively, when compared with CV treatment. However, it increased CH
4 and CO
2 emissions and resulted in an additional cost. 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 E. coli in all groups. However, the maximum temperature of the CV+RH pile can not reach 70 ℃, which had a minor impact on the mold inactivation efficiency. It was shown that manure fermentation covered with a functional membrane effectively controlled greenhouse gases and ammonia 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 standards. Membrane-covered fermentation of sole dairy manure residue is recommended for bedding material production, which can effectively reduce gas pollution and provide safe and comfortable bedding material for dairy farms.