Experimental study on dry anaerobic digestion of rice straw at ambient temperature in South China

After pretreated, dry anaerobic digestion technology with zymotic fluid circulated(total solid concentration is about 20%) for straw conversion to biogas was investigated. Biogas production, pH value, concentration of acetic acid and percentage of methane in ambient temperature digestion were tested. The result showed that the C/N adjustment and biological pretreatment reduced C/N from 37.18 to 28.01. The cumulative production in early 45 days was 80.4% of total production. The biogas production achieved 0.457 m³/kg TS. Compared with wet anaerobic digestion, the dry anaerobic digestion shortened the digestion cycle and increased the biogas production. The pH value in zymotic fluid was stable at 6.8～7.5 that can be accepted in anaerobic digestion. In digestion prophase, when the low percentage of methane continued in long period, inoculating again could increase the quality of biogas. This study could provide useful parameters for the design of large-scale dry anaerobic digester for straw conversion to biogas.