Aerobic and Anaerobic Two-phase Fermentation Process and Biogas Production Characteristic of Rice Straw

Abstract:

The main factor of hindering straw fermentation is lignocellulose hydrolysis due to the shielding effect of lignin. The shielding effect of lignin stops the extracellular enzymes of microorganisms getting in touch with cellulose leads to hydrolysis of acid fermentation process slowly. So the key to solving the bottleneck of the anaerobic fermentation process of straw is to damage the lignin structure in the hydrolysis stage and promote the contact of hydrolytic bacteria with the cellulose and hemicellulose. The reproductive capacity of aerobic microorganism is much higher than that of anaerobic microorganism and the initial cleavage of lignin requires the molecular oxygen. So the aerobic and anaerobic twophase fermentation process was put forward in order to improve the degradation rate of lignocellulose. The fermentation process was divided into aerobic hydrolysis fermentation and anaerobic methane fermentation in order to degrade lignocellulose of rice straw which was carried out at 37℃. Hydrolysis of acid fermentation tank was not sealed by stirring gas supply or non gas supply. The results showed that lignin structure of rice straw was damaged by aerobic and anaerobic twophase fermentation and higher lignin degradation rate was obtained. Lignin degradation rate of the stirring gas group was 4.57%, while degradation rate of lignin was only 0.13% at the end of the singlephase anaerobic fermentation. The highest biogas yield of TS was about 411.19mL/g at the stirring gas group 30% higher than the singlephase anaerobic fermentation. Therefore aerobic and anaerobic twophase fermentation process could effectively degrade lignin and increase biogas yield of TS.