Co-Digestion of Hog Manure with Glycerol to Boost Biogas and Methane Production

Abstract

The use of off-farm materials as amendments in anaerobic digestion of manure is an option that is being explored more extensively due to the benefits of boosting methane production and making the process more economical for the farmer. The addition of varying amounts of glycerol, which is a by-product in the biodiesel industry, was used as an amendment to anaerobic digestion of hog manure in bench-scale tests. The use of 2% glycerol produced the greatest amount of methane and biogas, while the addition of 4% glycerol resulted in an overloading of chemical oxygen demand (COD) and digester failure. The addition of 1% glycerol doubled the methane and biogas production, and there appeared to be no detrimental effects of using crude, industrial-based glycerol compared to pure, chemical-grade glycerol.