Production and use of biogas from dairy cow manure

The article describes an anaerobic digester built to produce electricity for a dairy from the manure of 350 cows. An insulated underground concrete reservoir, is a mesophilic, U-shaped, plug-flow type digester with a biogas mixing system. All biogas produced is fed to a 60 kw generator set. Wasted energy of the motor is used to heat the manure in the digester. A 600m**3 volume allows a retention time on 26 days with the present herd. Following a 12 month survey, it was found that the anaerobic digestion was very stable, despite operation variations found within farm situation and that this digester can produce more than 80% of the electric needs of the farm.