Hydrothermal and alkaline thermal pretreatment at mild temperature in solid state for physicochemical properties and biogas production from anaerobic digestion of rice straw

Abstract The effect of hydrothermal pretreatment (HTP) and alkaline thermal pretreatment (TA) at mild temperature in the solid state was comparatively studied, through the analysis of physicochemical properties of rice straw and its biogas production during anaerobic digestion. The results indicated that TA visibly increased the biogas yield from HTP. The accumulative biogas production of volatile solids was the highest for TA3 up to 411.1 mL/g VS, in which increased 24.04% compared to control. Therefore, the use of TA is more favorable to improve biogas production rates of anaerobic fermentation with rice straw than HTP, however, the additives of calcium hydroxide are too high, but it is not conducive to promoting the biogas yield of rice straw. The best additives amount of Ca (OH) 2 was 2% to consider the cost of pretreatment with straw. The research results provide technical support for pretreatment of anaerobic fermentation of lingo-cellulosic materials such as straw.