Investigation into the Biogas Production Potential of Dairy Cattle Manure

Abstract

We investigated the biogas production potential of dairy cattle manure obtained from the Fort Hare Dairy Farm, Eastern Cape Province of South Africa. A balloon type digester was charged with slurry of manure and operated under anaerobic digestion mode for six months. Fifty milliliters of slurry was withdrawn at different time intervals to analyze the microbial counts and physicochemical parameters by viable plate count method and standard methods, respectively. Data demonstrated that the pH and temperature ranged from 5.68-7.63 and 17.0 -25.04 o C, respectively. The total aerobic and anaerobic bacteria counts ranged from1.0 ×10 4 -7.5×10 6 and 4 ×10 2 -1.8×10 6 cfu/g, respectively, as well as the total yeast counts ranged from 2x10 2 - 1.0×10 6 cfu/g. A linear regression model was developed that predicted the relationship between log total bacteria count and average slurry temperature, pH and days of digestion. The 11.2% TS, 61.5% VS and 32.5 % ash content of the manure indicated that the dairy manure constituted of biodegradable portion. Biogas (4600cm 3 ) was produced during digestion and was combustible after 120 days. Thus, we concluded that dairy manure harbors a considerable level of anaerobic bacteria and methanogens that participated effectively to degrade the organic portion of manure generating renewable energy.