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Effect of H3PO4 Pretreatment on Biogas Production of Rice Straw during Anaerobic Digestion

To improve the gas production ability, relatively low cost H3PO4 was chosen as the pretreating agent in this study. Rice straws were pretreated by four different weight percentages (2%, 4%, 6% and 8%) of H3PO4 retting for seven days in an biochemical incubator at (25±1) °C, and the effects with different conditions of H3PO4 pretreatment on anaerobic digestion of rice straws for variation of components and anaerobic digestion performance (under temperature of (35±1) °C) were studied. The results showed that the peak value of biogas production was attained on the 1st day for using 6% H3PO4 pretreatment on rice straw, which is 2284 mL. The test daily methane content of different pretreatment conditions mainly ranges from 3.8% to 43.1%, with the highest recorded at the 12th day of the 2% H3PO4- treated rice straw. The cumulative biogas production of 6% H3PO4 pretreatment was the highest, about 16 474 mL.