2005 Volume 34 Issue 4 Pages 287-294
Continuous hydrogen fermentation from a mixed substrate containing carbohydrates, proteins and lipids was investigated using microflora. The experiment was conducted with a chemostat-type reactor at 35°C by using dog food with a constant TS concentration of 100g/L. The hydraulic retention time (HRT) changed from 6.4 to 34.5 hrs at a constant pH condition of 6.5. Continuous and stable hydrogen production was obtained for a long period, ranging from 6.4 to 34.5 hrs. The highest hydrogen production rate was found to be 1.18 L/L/d at an HRT of 12.8 hrs, while the highest hydrogen yield was found to be 0.24 mol-H2/mol-glucose at an HRT of 34.5 hrs. Both the hydrogen production rate and hydrogen yield were significantly lower than those in a batch experiment, indicating that the continuous hydrogen fermentation of the mixed substrate with chemostat-type reactor is difficult. On the other hand, the acidogenic efficiency increased with the increase in HRT, and 40% was obtained at an HRT of 34.5 hrs. The main acidogenic products were acetate and butyrate while some propionate and ethanol were also produced. The results of this study indicate that a long HRT, such as 34.5hrs, is necessary to obtain a high hydrogen yield and acidogenic efficiency for a mixed substrate of dog food.
