LAUSR

Abstract There are three steps (hydrolysis, acidification, and methanogenesis) involved in the anaerobic fermentation of organic matter, and the hydrolysis of macromolecular organic compounds is believed to be the key step. Biological hydrolysis and acidification is an important method for the utilization of rice straw (RS). The purpose of this study is to provide a novel, environmentally friendly and economical approach for promoting the hydrolysis and acidification of RS using waste activated sludge (WAS) as the inoculum and Gleditsia sinensis pod powder (GSPP) as the accelerant. The effects of adding GSPP on the hydrolysis-acidification performances of RS were explored through batch experiments. The achieved maximum concentration of the theoretical oxygen demand of volatile fatty acids (ThODVFAs) at a GSPP dosage of 0.030 g/g was 3836.1 mg/L, which was 85% higher than that without GSPP, and the ratio of the theoretical oxygen demand of acetic acid (ThODHAc) to ThODVFAs (ThODHAc/ThODVFAs) increased by 40% compared with that of a control with no GSPP. The addition of GSPP to a water soaking system of RS enhanced the release of organic matter from the RS, and the dissolved organic carbon (DOC) concentration on the 10th day increased by 50% compared with that of a control with no GSPP. The solubilization of GSPP saponins was beneficial to the surface pretreatment of RS by stripping the wax layer. This research concludes that the hydrolysis and acidification performances of RS can be effectively promoted by adding the natural surfactant GSPP.