Suitability of Canola Meal for Anaerobic Co-digestion of Dairy Manure

Abstract

Due to the renewed interest in the biogas production, co-digestion of livestock manure, especially dairy manure, and other agro-wastes has emerged as an appropriate technology in enhancing the economic viability of anaerobic digestion. In this study, various concentrations of canola meal and dairy manure rations (100% canola meal, 10% canola meal and 90% manure, 20% canola meal and 80% manure, 40% canola meal and 60% manure, and 100% manure) by volume basis were co-digested in 0.5L batch reactors at a temperature of 35±10C for 25 days. Pre- and post-digestion samples were collected and analyzed for nutrients, pH, volatile fatty acids, fibers and chemical oxygen demand (COD). Biogas yield was measured daily using the water displacement method and gas composition (mainly methane CH4) was analyzed weekly within 72 hours of collection using a gas chromatograph (HP 5890 Series II) flame ionization detector (FID). Results indicated that canola meal is not a potential candidate for anaerobic co-digestion with manure and have negative impact on biogas production. This is suspected to be caused by elevated levels of volatile fatty acids (VFAs) of more than 4000mg/L. It could be necessary to look into ways of overcoming the inhibition caused by elevated VFAs.