Anaerobic Digestion for Energy and Pollution Control

Anaerobic digestion is again being taken seriously because of increasing concernsabout the environmental hazards of manure. The push to produce more renewable energylocally to reduce dependence on fossil fuels has also had an effect. A well running plug-flowdigester on the Haubenschild dairy in Princeton, Minnesota has provided two continuous yearsof electrical energy production and operational data. Air pollution control and energy productioncoupled with the nutrient utilization are the reasons the digester project was installed atHaubenschild Farms. The 800 cows produce enough methane to generate about 2900 kWh perday of electricity, 1500 kWh of which is used on the farm. The remainder is sold as GreenEnergy and marketed to consumers who wish to use electricity generated from renewablesources. The digester is producing at least 30 percent more biogas beyond the design numbers.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 5years or less on investment is possible.