Anaerobic biodegradation of rice straw wastes for H-2 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 H-2 production rate (R-m). The results showed that the maximum R-m of 136.64 mlH(2)/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 H-2 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 H-2 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 H-2 production from pre-acidified rice straw. (C) 2012 Elsevier Ltd. All rights reserved.