Fermentative hydrogen production from tofu-processing waste and anaerobic digester sludge using microbial consortium

The combination of tofu-processing waste and anaerobic digester sludge was studied for its fermentative H2 production capacity in batch and continuous modes using a thermophilic mixed culture. Heat-treatment (110 °C, 30 min) in the presence of 0.5% HCl increased the soluble carbohydrate content of the tofu waste from 2.2 to 10.4 g/l. Anaerobic digester sludge was added to the tofu waste for supplementary nutrients with the optimal mixing ratio of 20% (v/v) under batch conditions. In continuous experiments, the effects of HRT(hydraulic retention time) and pH were investigated for the ranges of 2–6 h and 5.0–6.0, respectively. The maximal H2 production rate (12.0 l H2/l/day) and yield (2.3 mol H2/mol glucose equivalent) were obtained at HRT 4 h and pH 5.5 while maintaining the head space gas at 50–60% (v/v) of H2 without CH4. This study indicates that the combination of tofu-processing waste and digester sludge can be considered to be one of the most promising forms of organic waste for continuous H2 production.