Screening co‐digestion of food waste water with manure for biogas production

Abstract

AbstractAnaerobic digestion, an environmental protection technology for treating organic compounds in waste water, produces biogas, resulting in a renewable energy source. A protocol including waste analysis, waste blending, energy potential and energy balance calculations was developed to determine the energy production from blending food and animal wastes. Fruit and vegetable waste water produced from crop commodity processing was characterized in terms of quantity and 5‐day biochemical oxygen demand (BOD). Often these wastes have high levels of degradable carbon but lack buffering capacity and adequate nitrogen and other nutrients to meet the minimal C/N ratio needed for optimal digestion. Blending food‐processing waste water with high nutrient manure can enhance the biogas production by optimizing nutrient levels and providing buffering capacity. The protocol shows the procedure to determine the optimal blend and theoretical biogas production from the anaerobic digestion of that blend. An energy balance technique that determines the lowest COD concentration required to close the energy balance in the digester during different seasons is illustrated. A case study was conducted to determine the potential energy production from anaerobically digesting blended waste water from the top 14 fruit and vegetable commodities in Michigan. The resulting biogas production supports a substantial amount of the energy consumption needed for the treatment process. This case study in Michigan can be extended to national level since the calculations were based on the mean value of their typical range. © 2008 Society of Chemical Industry and John Wiley & Sons, Ltd