工艺措施对猪粪秸秆混合厌氧干发酵产气性能的影响

为避免挥发性脂肪酸积累、提高产气效率,研究猪粪单独发酵、猪粪秸秆混合发酵、猪粪秸秆混合原料分层接种和猪粪秸秆混合原料渗滤液回流等工艺措施下,中温(37℃)厌氧干发酵(总固体含量为20%)的产酸及产气性能。结果表明:猪粪秸秆混合原料分层接种厌氧发酵启动快,产气效果最佳,累积挥发性固体含量VS产甲烷量可达139.2mL/g;混合发酵渗滤液回流可有效降低总挥发性脂肪酸(total volatile fatty acids,TVFAs)质量浓度(维持在0.66 mg/g),累积VS产甲烷量比分层接种低16.7%;猪粪秸秆混合发酵与猪粪单独发酵的反应器中TVFAs质量浓度分别达到19.08和19.83 mg/g,前15 d日产甲烷量为0.1 mL/(g·d),基本不产气。通过不同工艺措施对比,获得产气量最高和启动期最快的发酵方式,提高猪粪厌氧干发酵产气效率,为猪粪等高固体含量有机废弃物的资源化处理利用提供参考。

Influences of different technological strategies on performance of anaerobic co-digestion of pig manure with straw in solid-state

Solid-state anaerobic digestion has advantages of water conversation, convenient management and low energy consumption in winter. After the digestion, substrate contains low water and can be easily treated, thereby achieving zero emission. Under the condition of increasingly scarce water resource in the world, this technology conforms to the demand of resource utilization and water conversation. However, the process of solid-state anaerobic digestion was very complex and the solid-state anaerobic digestion of pig manure could easily lead to serious accumulation of volatile fatty acids (VFAs), which was the main inhibiting factor in solid-state anaerobic digestion of pig manure. Due to the low water content, the reaction of solid-state anaerobic digestion could not proceed normally, or even be ceased. Several measures could be used to minimize the accumulation of VFAs. Leachate recycling was one way to accelerate mass transfer rate, and proper recirculation rate could optimize the digestion process and improve the quantity and quality of biogas. Stratified inoculation was an alternative method for solid-state anaerobic digestion, in which inoculum was separated with substrate layer by layer. The reaction hypothesis suggests that stratified inoculation could be used to decrease accumulation of VFAs, however, only a few studies had investigated its effect to decrease VFAs accumulation. This study was mesophilic batch fermentation under the same temperature (37 ℃) and water content (80%) condition. To investigate the most efficient treatment of starting the fermentation and the variations of methane production and VFAs, co-digestions of pig manure with maize straw, leachate recycling and stratified inoculation were carried out with the solid-state anaerobic digestion of pig manure as control. Ammonia nitrogen content and soluble chemistry oxygen demand were analyzed. The performances of VFAs production and methane production in the treatments of co-digestion with dried maize straw, leachate recycling, and stratified inoculation in solid-state anaerobic digestion of pig manure were compared. The results were as follows: The performances in stratified inoculation reactors were the best, characterized by no lag time, the highest methane yield of 9.4 mL/(g·d) and the highest cumulative methane yield of 139.2 mL/g; leachate recycling could retain TVFAs at a low level of around 0.66 mg/g, and its cumulative methane yield was 16.7% lower than the stratified inoculation treatment; the concentration of TVFAs in the co-digestion and mono pig manure digestion reactors reached 19.08 and 19.83 mg/g, respectively, and methane yield was less than 0.1 mL/(g·d) in the first 15 days in both reactors. The most efficient treatment with the highest methane production and the quickest initiating can be obtained by contrasting different treatments, which thereby provides the reference for environmental disposal and utilization of the wastes with high solid and high organic matter content.