Hydrogen and electricity production from a food processing wastewater using fermentation and microbial fuel cell technologies

Hydrogen can be produced from fermentation of sugars in wastewaters, but much of the organic matter remains in solution. We demonstrate here that hydrogen production from a food processing wastewater high in sugar can be linked to electricity generation using a microbial fuel cell (MFC) to achieve more effective wastewater treatment. Grab samples were taken from: plant effluent at two different times during the day (Effluents 1 and 2; 735±15 and 3250±90 mg-COD/L), an equalization tank (Lagoon; 1670±50 mg-COD/L), and waste stream containing a high concentration of organic matter (Cereal; 8920±150 mg-COD/L). Hydrogen production from the Lagoon and effluent samples was low, with 64±16 mL of hydrogen per liter of wastewater (mL/L) for Effluent 1, 21±18 mL/L for Effluent 2, and 16±2 mL/L for the Lagoon sample. There was substantially greater hydrogen production using the Cereal wastewater (210±56 mL/L). Assuming a theoretical maximum yield of 4 mol of hydrogen per mol of glucose, hydrogen yields were 0.61-0.79 mol/mol for the Cereal wastewater, and ranged from 1 to 2.52 mol/mol for the other samples. This suggests a strategy for hydrogen recovery from wastewater based on targeting high-COD and high-sugar wastewaters, recognizing that sugar content alone is an insufficient predictor of hydrogen yields. Preliminary tests with the Cereal wastewater (diluted to 595 mg-COD/L) in a two-chambered MFC demonstrated a maximum of 81±7 mW/m² (normalized to the anode surface area), or 25±2 mA per liter of wastewater, and a final COD of <30 mg/L (95% removal). Using a one-chambered MFC and pre-fermented wastewater, the maximum power density was 371±10 mW/m² (53.5±1.4 mA per liter of wastewater). These results suggest that it is feasible to link biological hydrogen production and electricity producing using MFCs in order to achieve both wastewater treatment and bioenergy production.