Fermentative bioenergy production from distillers grains using mixed microflora

The feasibility of hydrogen production from distillers grains substrate, an industrial cellulosic waste, was investigated. A substrate concentration of 80 g/L gave the maximum production at 50 °C and pH of 6.0 using sewage sludge. Four controllable factors with three levels: seed sludge (two sewage sludges and cow dung), temperature (40, 50, and 60 °C), pH (6, 7 and 8) and seed pretreatment (none, heat, and acid) were selected in Taguchi experimental design to optimize fermentation conditions. The peak hydrogen and ethanol productions were found with heat-treated cow dung seed, substrate concentration 80 g/L, 50 °C and pH 6. The peak hydrogen production rate and hydrogen yield were 7.9 mmol H2/L/d and 0.40 mmol H2/g-COD respectively whereas the peak ethanol production was 3050 mg COD/L and rate 0.22 g EtOH/L/d. A total bioenergy yield of 41 J/g substrate was obtained which was 21% and 79% from hydrogen and ethanol respectively.

► Distillers grains could be hydrolyzed and converted into H2 and ethanol.
► Seed sludge, seed pretreatment, pH and temperature influenced H2 production.
► Seed inoculum and seed pretreatment had stronger effect on ethanol production.
► Peak H2 and ethanol production was by using heat-treated cow dung.
► Substrate concentration 80 g/L, 50 °C and pH 6 were optimum for H2 and ethanol.