Production of Biogas by Using Different Pretreatments of Rice Straw Under Aerobic and Semi Aerobic Conditions.

Hared lignocellulosic structure of rice straw is the main hindrance in biogas production process. Thus, laboratory scale batch experiment was conducted to study the effect of different pretreatments of rice straw on anaerobic digestion. For this reasons, different pretreatments of rice straw prior anaerobic digestion was run using chemical activator, cattle dung, Tricoderma viride, phanerochaete chrysosporium and effective microorganisms under aerobic and semi aerobic conditions to study the effect of these pretreatments on the speed and production of biogas. The results indicated that semi aerobic pretreatment has significantly increased the production of biogas more than aerobic pretreatments. The highest yield of biogas and methane production were obtained after anaerobic digestion process at three days from pretreatments. Pretreatment T4 (rice straw + cattle dung + effective microorganisms + starter) achieved in semi aerobic in biogas and methane higher than aerobic pretreatments where, obtained 9.37, 5.94 L biogas and 5.42, 3.22 L methane, respectively. Biogas and methane production rates were based on either total solid or volatile solid where, ranged between 46.60- 381.83 L/Kg consumed biogas and 18.98- 220.86 L/Kg consumed methane. Volatile fatty acids concentration were increased during pretreatments to reach the highest concentration after three days, then decreased subsequently, meanwhile the concentration decreased after anaerobic fermentation process. Also, the pH values increased at the end of anaerobic digestion the values ranged between 7.02-8.28.Ammonical- N concentration was decreased during pretreatments to reach its lowest the concentration after seven days, then decreased at the end of fermentation process where, ranged between 23-138 mg/Kg in final anaerobic digestion process. Pretreatment T4B3 (rice straw + cattle dung + effective microorganisms + starter) after three days from semi aerobic led to the best biogas manure which contents much humic substances.