Pretreatment of rice straw for increasing the biodegradability

This research is aimed at the development of cost effective pretreatment technologies that will enable faster and more efficient degradation and conversion of lignocellulosic biomass into biofuel and other valuable products.;Orthogonal experimental design was used to determine the effects of three key factors (alkali chemical, alkali loading and temperature). Alkali (Ca(OH) 2, NaOH, KOH) loading was tested at 2%, 6%, and 10% levels (based on dry biomass), and temperature was 20, 35, and 50°C. The results show that NaOH treatment at 20°C and with 10% chemical loading achieved the highest lignin removal of 35%. Temperature ranging from 20°C to 50°C had no significant effect on lignin removal. With 23 day anaerobic digestion at mesophilic temperature of 35°C, rice straw pretreated with 10% NaOH at 20°C for 24 hours had the biogas yield of 0.6 L/g VS, 50% higher than the biogas yield from untreated straw. The pretreated straw had the reducing sugar yield of 298 mg glucose/g VS, 185% higher than the untreated straw.;The results from the above experiments were used to design experiments for optimization of pretreatment conditions. Rice straw was treated with different amounts of NaOH at 20°C for the duration of 1-3 days. No significant difference was observed among three time levels tested. Rice straw treated by 10% NaOH for 2 days achieved the maximal values of cumulative biogas yield of 0.57 L/g VS. Statistic results show treatment with 10% NaOH had significantly higher biogas yield than treatment with 6% and 14% NaOH. Rice straw treated by 14% NaOH for 2 days reached the maximal values of glucose (335 mg/g VS) after enzymatic hydrolysis. No significant differences were observed on glucose yield for the three time levels.;Net energy and economic analysis were conducted to determine the feasibility of a proposed rice straw pretreatment and processing system. A 10,000 ton/year rice straw pretreatment and processing plant was designed based on the laboratory research results. 11244 MJ/ton FFE surplus and energy yield ratio of 4.0 could be achieved. Sensitivity analysis results show that the economic model is most sensitive to the changes in the biogas yields and rice straw treatment capacity.