Abstract
This study was conducted to compare the performances of batch and continuous hydrogen fermentation of a mixed substrate (dog food) using a microflora. Hydrogen gas production, substrate decomposition, and metabolic pattern were evaluated for the comparison. The batch reactor was operated at 35°C with a constant pH (ranging from 4.0 to 7.5) and various substrate concentrations (TS 2%, 5% and 10%) . Hydrogen fermentation was greatly affected by pH at each TS concentration and the optimal pHs for obtaining maximum hydrogen yield were identified to be 4.5-5.5 for TS 2%, 5.5 for TS 5% and 6.5 for TS 10%. The maximum hydrogen productions at TS 2 %, TS 5 % and TS 10% ranged from 93.9 to 108 mL/g-VS. The H2 yield at the optimal pH was as high as 1.80 mol-H2/ mol-glucose. Butyric acid and acetic acid were the main products at optimal pH, while a complex fermentation pattern was obtained at a pH close to 4.0 or 7.0. In another experiment, the continuous hydrogen fermentation was conducted at 35°C, TS 10%, pH 6.5 and various HRT (from 6.4 to 36.5 hour) . The maximum hydrogen production in the continuous fermentation was as low as 0.21 mol-H2/mol-glucose, which was obtained at an HRT of 12.8 hours. The experimental results indicate that in treating mixed organic wastes continuous hydrogen fermentation is more difficult than batch fermentation.
