奶牛场粪渣覆膜发酵生产垫料气体排放和病原菌变化

Gas emissions and pathogen dynamics during bedding material production based on membrane-covered fermentation of dairy manure residue

  • 摘要: 采用牛粪渣好氧发酵再生垫料是奶牛场粪污处理的重要模式, 但是高温发酵造成大量碳氮气体排放, 亟待进行减控。本研究在大型奶牛场现场开展原位试验, 设置牛粪渣+不覆膜处理(CK)、牛粪渣+覆膜处理(CV)和牛粪渣混合稻壳+覆膜处理(CV+RH), 监测其在12天的完整发酵过程中不同温室气体(GHG)和氨气(NH3)排放规律, 探究不同处理对气体排放和垫料灭菌效果的影响。结果表明, CK、CV和CV+RH处理堆体NH3累积排放量分别为23.4、1.0和0.2 g/m2, CO2累积排放量分别为10.48、6.01和7.65 kg/m2, CH4累积排放量分别为52.6、33.3和42.1 g/m2, N2O累积排放量分别为93.1、68.3和38.6 mg/m2。与CK处理相比, CV处理堆体NH3、CO2、CH4、N2O和总GHG累积排放量分别减少95.7%、42.7%、36.7%、26.6%和36.6%; 与CV处理相比, CV+RH处理堆体NH3和N2O的累积排放量分别减少80.0%和43.5%, 但是会增加CH4和CO2累积排放量各处理试验过程沙门氏菌和金黄色葡萄球菌均未检出, 垫料高温发酵过程实现了对各处理粪大肠杆菌的有效杀灭, 但CV+RH处理堆体最高温度一直低于70 ℃, 对霉菌的灭杀效果略有影响。功能膜覆盖能够有效阻控牛粪渣发酵产生的GHG和NH3, 是解决奶牛场垫料发酵气体污染的重要手段, 而覆膜后再添加稻壳对GHG整体减排效果的提升不明显, 两种技术产出的垫料均符合垫料标准对病原菌指标的相关要求。推荐以单一牛粪渣作为发酵原料, 结合覆膜好氧发酵技术生产再生垫料, 以有效减少粪便发酵过程中的污染气体排放, 为牛场提供安全舒适的垫料。

     

    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 m3. 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 m3/(min·m3 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 NH3 were 23.4, 1.0 and 0.2 g/m2 in CK, CV, and CV+RH, respectively, 10.48, 6.01and 7.65 kg/m2 for CO2, 52.6, 33.3 and 42.1 g/m2 for CH4, and 93.1, 68.3 and 38.6 mg/m2 for N2O. Compared with CK treatment, the cumulative emissions of NH3, CO2, CH4, N2O, 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 NH3 and N2O by 80.0% and 43.5%, respectively, when compared with CV treatment. However, it increased CH4 and CO2 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.

     

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