investigation of chemical pretreatment of rice straw with ammonia, urea and sodium hydroxide

agricultural residues have high potential to produce biogas, but they contain lignocellulosicmaterials which are not easily degradable, so the pretreatment is required. chemical pretreatmentincreases the rate of degradation and efficiency of biogas production. this study has beeninvestigated the effect of 4% -urea, 5%-ammonia and 8%-sodium hydroxide on degradation of ricestraw and production of biogas combined with sheep manure with three carbon to nitrogen ratios(15, 20 and 29) in anaerobic digester at temperature of 40±2 °c. the process was performed in afactorial design with two factors in three replications. results showed that the cumulativeproduction of biogas and the maximum percent of methane are 594 (ml/vsadd ) (that is 133.33%more than the control) and 71% that they achieved by 8%-naoh-pretreated straw combined withmanure in carbon to nitrogen ratio of 29. the results show the positive effect of chemicalpretreatment of rice straw on efficiency of biogas production combined with sheep manure.