The Feasibility of Shortening the Pretreatment Time for Improvement of the Biogas Production Rate from Rice Straw with Three Chemical Agents

Solid-state chemical pretreatment at room temperature was adopted to evaluate the methane production potential of rice straw. Dried rice straw was homogenized with distilled water at a 1:3 ratio and pretreated for 6 h, 24 h, 72 h, 120 h, and 168 h. The effects of the pretreatment time with three chemicals (H2O2, Ca(OH)2, and NH3·H2O) on the methane yield were investigated. The results showed that the anaerobic digestion performance was improved for solid-state chemical pretreatment of room temperature-treated rice straw. The biogas yields from the treatments with H2O2 for 168 h, Ca(OH)2 for 72 h, and NH3·H2O for 120 h were 386.6 mL/g VS, 413.5 mL/g VS, and 390.5 mL/g VS, which were 35.8%, 45.2%, and 37.2% higher than that from the untreated rice straw, respectively. Therefore, it is feasible to shorten the pretreatment time of rice straw for these three chemical solutions.