Optimum hydraulic retention time for dark-fermentative hydrogen production from co-digestion of vinasse and dried spent yeast

Abstract

Utilization of vinasse, wastewater from ethanol distillation process, for dark-fermentative hydrogen production was demonstrated in this research. The objective of this research was to optimize the hydraulic retention time (HRT) of hydrogen production from co-digestion of vinasse and dried spent yeast. The experiment was conducted in lab-scale reactors with a working volume of 5 L. Hydrogen production rate, pH and volatile fatty acids (VFAs) in the effluent of hydrogen production were studied during the optimization of HRT. Fly ash was used as an additive to stabilize the pH of fermentation. Results revealed that the optimum HRT for hydrogen production was 1 d. The maximum hydrogen production rate of 1,418 mL/L.d was obtained. The VFAs contents in hydrogen production effluent were different when the HRTs were varied, revealing the changes in fermentation pathways. Thus, the VFAs contents in hydrogen production effluent can be used as a good indicator for monitoring hydrogen production efficiency. Moreover, fly ash showed an effective pH control with an average pH of 5.41, which is the optimum range for dark-fermentative hydrogen production.