Anaerobic Digestion for Energy and Pollution Control

Anaerobic digestion is again being taken seriously because of increasing concerns about the environmental hazards of manure. The push to produce more renewable energy locally as a means to reduce dependence on fossil fuels has also had an effect. A well running plug-flow digester on the Haubenschild dairy in Princeton, Minnesota has provided nearly five continuous years of electrical energy production and operational data. The digester was initially installed at Haubenschild Farms to control air pollution and to produce energy by utilizing waste. The 800 cows at the farm produce enough methane to generate about 2900 kWh per day of electricity, 1500 kWh of which is used on the farm. The remainder is sold as "Green Energy" and marketed to consumers who wish to use electricity generated from renewable sources. The digester is producing at least 30 percent more biogas than the design estimates. The dairy also saves $400 per month in heating costs by using waste heat from the generator. The up time on the generator has been about 95%. This project has shown that a payback of 5 years or less on investment is possible.