碱处理对秸秆厌氧消化的影响

为减少秸秆碱处理的碱用量,提高秸秆的产气量,从产气量、XRD和FTIR等角度对碱预处理与后处理进行了初步比较,并对碱处理前后秸秆浸提液的理化性质以及秸秆的物质结构变化进行了分析.结果表明,秸秆经5%NaOH处理48 h后,细胞中的有机物大量溶出,COD、TN、NO 3--N和NH 4+-N分别从2 311.11、175.40、5.02和117.82 mg/L增至10 488.89、417.84、248.64和141.44 mg/L,表明碱处理不仅破坏木质纤维结构,还破坏核酸、氨基酸等含氮物的结构,将其中的氮以NO 3--N和NH 4+-N的形式释放出来;碱处理破坏了秸秆木质素结构,木质素含量降低,但纤维素的相对结晶度增加,从0.592 3增加到0.662 2.厌氧消化的结果显示,秸秆预处理与后处理的产气能力相当,单位TS产气量分别为382.32 mL/g和375.84 mL/g,较对照分别提高了28.13%和25.96%,但后处理的碱用量仅为预处理的50%;厌氧发酵后对照中的木质素含量增加,而预处理和后处理均降低,后处理对木质素的破坏效果更好;厌氧微生物可破坏纤维素的结晶区,后处理对纤维素结晶区和无定形区的破坏均强于预处理.

Effect of Alkaline Treatment on Anaerobic Digestion of Rice Straw

The biogas yields of rice straw during anaerobic digestion can be improved by alkaline pretreatment, while it increased the cost because of large amount of alkaline. In order to decrease the amount, 3 sets of experiments were performed using straw with alkaline treatment (pretreatment), digested straw with alkaline treatment (post-treatment) and straw digested directly (control). The results showed that cell wall of straw was destroyed by 5% NaOH treated for 48h, the COD (chemical oxygen demand), total nitrogen, NO^-₃-N and NH⁺_4-N were increased from 2311.11, 175.40, 5.02 and 117.82 mg/L to 10488.89, 417.84, 248.64 and 141.44 mg/L respectively. It suggested that not only lignocellulose but also some nitrogenous materials were destroyed or broken down by alkaline treatment. The lignin structure was destroyed through alkaline treatment that caused the decreased lignin, but the crystallinity index (C_rI) of cellulose increased from 0.5923 to 0.6622. The results of anaerobic digestion showed that the total solid of straw decreased 50.47% after anaerobic digestion treatment leading to less workload and only 50% alkaline used. However, the biogas yield of post-treatment and pretreatment were 382.32 mL/g of TS_added and 375.84 mL/g of TS_added. Lignin content of control increased while decreased in pretreatment and post-treatment. After anaerobic digestion, crystalline of cellulose was destroyed significantly, and crystalline and amorphous of post-treatment were destroyed more severely than that of pretreatment. From all those mentioned above, post-treatment of straw with alkaline was economical and feasible for biogas production.