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Cow-Powered Biogas Energy

09 October 2008

US - Focus on Energy has released the Wisconsin Agricultural Biogas Casebook, an online report which includes case studies of 17 dairy farm anaerobic digesters that produce renewable energy.

Wisconsin currently leads the nation in the number of operating dairy farm digesters that produce electricity and heat from cow manure and other organic materials.

The report offers a historical snapshot of the current operating digester systems on Wisconsin farms and is meant to give those interested in digesters some insight on how to implement their own system.

"We're very proud of the leadership role Wisconsin farms have played in the field of digester systems," said Larry Krom, project manager for Focus on Energy.

"Many of the projects in the casebook received funding from Focus on Energy. It's our hope that farms from across the state will look to this casebook as a resource. It offers many project details on how different digester systems work, describes enhancements by farm operators and includes candid observations from the farmers themselves."

When a farm installs an anaerobic digester, it offsets its energy consumption and contributes electricity to the local electrical grid. The projects have a positive effect on the environment by reducing fossil fuel use, substantially eliminating all manure odors and pathogens and better controlling the final waste product.

As an example, a typical anaerobic digester with a 300 kilowatt biogas-fueled generator will produce enough electricity to power 224 average Wisconsin homes. In addition, the annual environmental benefits would be equivalent to offsetting 1,117 tons of coal from being burned, the emissions from 361 cars, or nearly 2,460 tons of the greenhouse gas carbon dioxide from being released into the atmosphere.

Anaerobic digestion is the bacterial decomposition of organic matter that occurs in the absence of oxygen. An anaerobic digester system is an enclosed tank that excludes oxygen and through which organic matter is passed and broken down by naturally occurring bacteria, producing biogas.

This biogas is composed of approximately 55 per cent to 70 per cent methane. The methane produced in the process can be used in an engine-generator to produce electricity and heat.

In addition to producing electricity, a farm anaerobic digester can help manage animal waste. They also help to control odors, preserve the environment and produce valuable byproducts in the form of organic fertilizers.

Further Reading

- You can view the full report by clicking here.

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