This is an excerpt from EERE Network News, a weekly electronic newsletter.

January 17, 2007

Reports Note Lessons Learned for Five Dairy Manure Digesters

Anaerobic digesters are gaining popularity throughout the United States as a means to convert manure to methane, which can fuel an electrical generator. The technology is particularly appealing to dairy farmers, since it provides a means of disposing of manure and avoiding odors while creating a usable energy source. But before taking the plunge themselves, dairy farmers would be well advised to study five evaluation reports on new dairy digester systems that were issued by the California Energy Commission (CEC) in December.

The five dairy farmers experienced a number of challenges with their new systems, including delays and cost overruns; lack of funds due to a drop in milk prices; reduced herds that produced less manure; troubles obtaining construction and utility interconnection permits; difficulty staying connected to the utility grid; inability to connect the largest dairy power loads to the generator; difficulty avoiding demand charges due to system down time; financial woes due to inadequate net metering arrangements; and equipment problems.

Despite the challenges, though, the systems demonstrated the ability to produce ample biogas and electricity, although all of the farmers ended up flaring much of their biogas instead of producing power. The farmers generally found the systems useful for manure and odor management, but some struggled with the operation of their systems and most were unable to make the best use of the energy provided by their systems. With net metering laws and demand charges often not working to their advantage, it seems that most farmers would be best served by trying to power their farm with their generators, rather than counting on benefits from feeding the power into the electrical grid. See the five dairy reports on the CEC Web site.

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