非混合接种对猪粪厌氧干发酵产气特性的影响

为达到缓解猪粪厌氧干发酵时有机酸的积累并能够同时提高产气性能的目的，采用小试批式实验，在中温(37 ℃)、总固体(TS)为20%的条件下研究了猪粪接种物全混合发酵、猪粪非混合接种发酵、猪粪玉米秸秆与接种物全混合发酵及猪粪玉米秸秆混合原料非混合接种发酵这4种方式对发酵体系的有机酸积累及产甲烷特性的影响。结果表明，猪粪接种物全混合发酵和猪粪玉米秸秆与接种物全混合发酵的总有机酸(TVFAs)质量浓度在发酵结束时分别为15.2和3.6 mg·g⁻¹，较对应底物的非混合接种发酵分别提高了6.3倍和5.0倍。在2种非混合接种发酵体系中，TVFAs质量浓度在21 d后迅速降低。其中，猪粪玉米秸秆混合原料非混合接种的TVFAs下降幅度更大，其第30天的TVFAs质量浓度低于1.5 mg·g⁻¹。猪粪玉米秸秆混合原料非混合接种厌氧发酵产气效果最佳，累积VS产甲烷量达到148.2 mL·g⁻¹。猪粪非混合接种发酵沼气中甲烷含量最高，达到75.1%。修正的Gompertz模型拟合结果显示，猪粪玉米秸秆混合原料非混合接种发酵和猪粪非混合接种发酵的迟滞期分别为10.6和12.4 d，较对应底物的混合接种发酵分别缩短了5.9和6.1 d；最大VS产甲烷速率分别提高了1.7倍和4.9倍，达到6.2和4.8 mL·(g·d)⁻¹。非混合接种能够缓解猪粪厌氧干发酵的酸抑制并同时提高其甲烷产率。

Effects of non-mixed seeding on methane production characteristics of the batch dry anaerobic digestion of pig manure

In order to alleviate the accumulation of organic acids and enhance the methane production, a small batch experiment was performed in a self-made vertical plexiglass reactor under mesophilic temperature of 37 °C and total solids (TS) of 20%. Pig manure was used as major substrate with different seeding ways including full mixed seeding digestion and inoculum, non-mixed seeding digestion, full mixed digestion maize straw and inoculum, and non-mixed seeding digestion of mixed pig manure and maize straw. The results showed that the mass concentration of total volatile fatty acids (TVFAs) were 15.2 mg·g−1 and 3.6 mg·g−1 with the seeding ways of mixed seeding digestion of the full mixed seeding digestion of pig manure and full mixed raw materials of pig manure and maize straw respectively, which were 6.3 times and 5.0 times higher than that of the corresponding non-mixed seeding raw materials. In the non-mixed seeding system, the TVFAs mass concentration rapidly decreased on day 21. Particularly, the TVFAs mass concentration of the pig manure and straw mixed raw material was lower than 1.50 mg·g−1 on day 30. In addition, the methane yield of non-mixed seeding digestion of the mixed raw materials of pig manure and maize straw reached a highest value of 148.2 mL·g−1, along with a highest methane content of 75.1%. The fitting results of the modified-Gompertz model showed that the fermentation lag time of non-mixed seeding digestion of the mixed raw materials of pig manure and maize straw and non-mixed seeding digestion of pig manure were 10.6 days and 12.4 days respectively, which were 5.9 days and 6.1 days shorter than that of corresponding mixed seeding raw materials. Moreover, the cumulative methane yields reached 6.2 and 4.8 mL·(g·d)−1, respectively, which was increased by 1.7 times and 4.9 times. These results demonstrated that the non-mixed seeding could effectively alleviate the organic acid inhibition and increase methane yield during the dry anaerobic digestion of pig manure.