With people looking for alternative energy sources, anaerobic digesters have become a topic of interest, especially for livestock producers with plenty of raw material -- namely manure. Gene McClure, OSU Extension Educator ANR, Hardin County, recently attended a program hosted by the Ohio Rural Electric Cooperatives on the topic of converting methane to electricity by way of anaerobic digesters. He sent out a memo to all educators sharing a bit of what he found.

McClure found out there are two farms, one poultry and one dairy, with anaerobic digesters which are currently generating electricity in Ohio. Both farms are selling the power to Buckeye Power, Ohio's Electric Cooperative power generation and transmission organization. The farms then purchase their electric power from their local cooperative electric distribution system. McClure also found out some of the benefits and challenges of using this technology.

Large amounts of manure or other organic wastes are required in order to provide the steady supply of raw materials that need to be added to the system on a regular basis. It appears at least 500 cows or 3,000 hogs are needed before methane/ electric generation is to be considered.

In addition, there needs to be some management considerations regarding these raw materials, as the process can be upset by various variables, such as antibiotics or other medical treatment of the animals, adding other organic material such as food wastes, which have been washed with various cleaners or even low temperatures in the environment. One option to help with the temperature is to use some of the methane produced to maintain the heat of the manure in the digester to nearly 100 degrees to keep the digester running at peak efficiency.

The methane could also be used for other heating purposes, but it needs to be realized the biogas produced is only about 60 percent methane with the rest consisting of CO2, water vapor, ammonia and hydrogen sulphide, which can be corrosive to pipes and engines. The hydrogen sulphide is also the main cause for problem odors. Generating and collecting the biogas from the manure with an anaerobic digester has been shown to reduce these offensive odors. This alone in some cases has been the justification of building a system, even if the methane is flared off or burned at the site.

The cost of putting in a digester is expensive, though some grant- subsidized funds may be available to help do so, as the public has interest in finding new effective ways to generate renewable energy. And if you do use methane for generating electricity to sell back to the electric companies, there are federal regulations that need to be complied with, as well as entering into a power purchase agreement with the power company.

So where do you start if you are interested in producing electricity from methane? McClure suggests contacting your electric co-op or distribution company to visit with electrical engineers who work in the area of electric generation and transmission for more precise details of the requirements. Two reliable contacts are Don Leis, Senior Power Deliver Engineer with Buckeye Power (614-846- 5757) and Richard Hiatt with the Rural Electricity Resource Council in Wilmington (937-383-0001).

Ron Becker is an OSU Extension program coordinator.

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