Factors affecting hydrogen production from rice straw wastes in a mesophillic up-flow anaerobic staged reactor

Anaerobic biodegradation of rice straw wastes for H2 production via mesophillic up-flow anaerobic staged reactor (UASR) was investigated. Two batch experiments were carried out. The 1st experiment was conducted to assess the effect of pre-acidification process on H2 production rate (Rm). The results showed that the maximum Rm of 136.64mlH2/h was achieved for pre-acidified (0.72%) rice straw waste, which was approximately 28.64-fold greater than that in untreated rice straw. The H2 content in the biogas was 52.0% and there was no significant methane observed in this study. The pre-acidified rice straw was used for subsequent experiments concerning the influences of environmental factors such as pH, contact time, and substrate concentration on H2 yield (HY). Trends indicate that both high and low-end pH is unfavorable and substrate concentration of 30 g COD/l and contact time of 30 h is recommended for H2 production from pre-acidified rice straw. ► Up-flow anaerobic staged reactor is a promising technology for hydrogen production. ► Acid pretreatment is efficient for hydrogen production from rice straw waste. ► The H2 content in the biogas was 52.0% and there was no methane produced. ► The reactor achieved a maximum H2 production rate of 140.66 ml H2/h. ► Both high and low pH is unfavorable for hydrogen production from rice straw.