Fermentative hydrogen production from cassava stillage was conducted to investigate the influences of temperature (37 degrees C, 60 degrees C, 70 degrees C) and initial pH (4-10) in batch experiments. Although the seed sludge was mesophilic anaerobic sludge, maximum hydrogen yield (53.8 ml H(2)/gVS) was obtained under thermophilic condition (60 degrees C), 53.5% and 198% higher than the values under mesophilic (37 degrees C) and extreme-thermophilic (70 degrees C) conditions respectively. The difference was mainly due to the different VFA and ethanol distributions. Higher hydrogen production corresponded with higher ratios of butyrate/acetate and butyrate/propionate. Similar hydrogen yields of 66.3 and 67.8 ml H(2)/gVS were obtained at initial pH 5 and 6 respectively under thermophilic condition. The total amount of VFA and ethanol increased from 3536 to 7899 mg/l with the increase of initial pH from 4 to 10. Initial pH 6 was considered as the optimal pH due to its 19% higher total VFA and ethanol concentration than that of pH 5. Homoacetogenesis and methonogenesis were very dependent on the initial pH and temperature even when the inoculum was heat-pretreated. Moreover, a difference between measured and theoretical hydrogen was observed in this study, which could be attributed to homoacetogenesis, methanogenesis and the degradation of protein. (C) 2010 Elsevier Ltd. All rights reserved.