基于秸秆后发酵产沼气的一次发酵时间优化

采用“一次发酵+ NaOH处理+二次发酵”工艺,以稻秸为原料,研究一次发酵时间对稻秸沼气发酵的影响.结果表明,一次发酵后的稻秸仍有一定的产气能力,干物质(TS)产气量为28.11~50.73mL/g TS,产气量大小与一次发酵时间成反比;一次发酵后的稻秸经NaOH处理后,稻秸物质结构受到明显破坏,有机物大量溶出,稻秸浸提液COD、总氮、铵态氮和硝态氮浓度分别较未经NaOH处理的稻秸提高128.56%~213.62%、93.92%~110.59%、53.90%~73.78%和112.08%~188.98%;NaOH处理并不能破坏稻秸的骨架结构,但稻秸官能团相对含量发生变化,加剧了纤维素、半纤维素和木质素结构的破坏.将一次发酵15,25和35d的稻秸经NaOH处理后用于沼气发酵,产气量较相应的对照分别提高了77.37%,119.41%和159.94%,一次发酵时间越长NaOH处理促进秸秆产气的效果越好.实验结束时,一次发酵15,25和35d的稻秸总产气量分别为202.78,205.15,210.21mL/g TS,三者间差异不显著,但较对照(CK)显著提高了11.89%、13.20%、15.99%,发酵周期较CK分别增加了-12,-2,8d.综上所述,采用“一次发酵+ NaOH处理+二次发酵”工艺时,一次发酵时间选择15d更合适.

Optimization of the first fermentation time based on biogas post-fermentation with rice straw

To solve the problems of low chemical treatment efficiency and high treatment cost caused by entanglement of cellulose, hemicellulose and lignin in straw, the process of "first fermentation + NaOH treatment + secondary fermentation (PNS)" was adopted, and the effect of primary fermentation time on biogas production of straw was studied. The results indicated that the digested rice straw could still be used for biogas production with total solid (TS) biogas yield of 28.11-50.73mL/g TS, and the biogas yield was inversely proportional to first fermentation time. After the NaOH treatment, the material structure of digested rice straw was obviously damaged and a large amount of organic matter was leached out. The concentrations of COD, TN, NH₄⁺-N and NO₃^--N in the rice straw leachate were significantly increased by 128.56%~213.62%, 93.92%~110.59%, 53.90%~73.78% and 112.08%~188.98%, respectively, compared with those without NaOH treatment. NaOH treatment did not destroy the skeletal structure of digested rice straw, but changed the relative content of functional groups of digested rice straw, which intensified the destruction of cellulose, hemicellulose and lignin. After first fermentation of 15, 25, 35d and NaOH-treatment, the digested rice straw were reused for biogas production. The TS biogas production of digested rice straw were increased by 77.37%, 119.41% and 159.94%, respectively, compared with that under control treatment. The longer primary fermentation time, the better effect of promoting biogas production. After the experiment, the total biogas yield of rice straw of the treatment of primary fermentation time with 15, 25 and 35d were 202.78, 205.15 and 210.21mL/g TS, respectively, which were significantly increased by 11.89%, 13.20% and 15.99% compared with that of correspending control, and the total fermentation time were extended by -12, -2 and 8days. In summary, when adopting the process of PNS, the primary fermentation time of 15d is suitable.