Methane to Electricity

Below is a guest post from Gene McCluer, OSU Extension Hardin County Extension Educator:

As a source of renewable energy, there is much interest in converting manure into methane and the methane into electricity. There are two farms with anaerobic digesters which are currently generating electricity in Ohio. Both farms are selling the power to Buckeye Power, Inc., Ohio’s Electric Cooperative power generation and transmission organization, and then purchasing their electric power from their local cooperative electric distribution system. These pilot projects are at Wenning Poultry in Mercer County and Bridgewater Dairy in Williams County. Here are some key points

1. We know how to generate and collect methane from manure. The process, however, can be upset by various things, 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, low temperatures, and many more. When the system is upset, methane generation is reduced and generation is affected. There is a definite need for an operation and management expertise component to these systems.

2. The cost of building an on-farm system is large, but the exact costs are not easy to find. In almost every case we heard about, there was some grant subsidized funds include, as the public has interest in finding new effective ways to generate renewable energy.

3. The farmers in Ohio who are operating the demonstration sites are large operations. One farm has more than 800,000 layers and the other operates a 4,000 head dairy farm. It seems that a large volume of manure generation is necessary, and a steady supply of new manure or other organic wastes needs to be added to the system on a regular basis. It appears that at least 500 cows or 3000 hogs are needed before methane/generation is to be considered.

4. The “biogas” generated is not equal to propane or natural gas. It typically includes about 60% methane, 35% CO2, some water vapor, ammonia, and hydrogen sulfide. Methane is the only portion that burns, and some of the other components are quite corrosive to pipes and engines. Preventing the release of “greenhouse gases” can generate carbon credits, which have value.

5. Generating and collecting the biogas from the manure with an anaerobic digester has been shown to reduce the offensive odors of the manure. 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. That is how big solving a manure odor problem can be in some farm situations.

6. Utilizing the biogas to generate heat may also be an important use of the methane, if there is a need for heat energy on the farm or nearby. Serious digester operators utilize some of the heat to maintain the manure in the anaerobic digester at about 100 deg. F. to maximize the biological generation of biogas.

7. The biogas can power an engine/generator to generate electricity. The electricity can be used on the farm, with the appropriate electric configuration approved by the electric distribution company providing the normal power for the farm. With self generated power, there must be a standby power arrangement with the electric company for when the generator is down for maintenance or other incidental problems in the system occur. This is likely to cause the farm to have a higher electric rate, since the power company still has the expense of installing and maintaining all of the equipment to operate the farm, even though they may not sell power there on a regular basis. I think this may be part of the reason that the two Ohio farms are selling all of their power and purchasing the power from the local electric coop distribution company.

8. Connecting to the grid and selling electricity is not as easy as it sounds. All electric generators that interconnect to the power grid, regardless of size, are required to file an application or self-certification with the Federal Energy Regulatory Commission (FERC) to obtain “qualifying facility” status under the Public Utilities Regulator Policies Act (PURPA), and must apply to the local electric utility for interconnection to the lines. If the farm wants to “self-supply” (use the electricity that it generates) and generates more than they use in a year, they must enter into a Power Purchase Agreement with Buckeye Power. If the output of the generation exceeds the usage of the consumers on the local utility’s distribution circuit, or, they connect directly to the transmission system, they must also enter into a Wholesale Market Participation Agreement with the transmission owner and the transmission operator before power can be put on the transmission lines. There are many more permits, agreements, and studies which need to be completed before a farm can generate electricity for the grid.

9. There is a significant equipment requirement needed to interconnect the generator to the electric power grid. Most of this equipment either measures the amount sold to the power company or to synchronize the electric voltage, frequency, and phase with the line it is being connected to. Other switchgear equipment is required to make sure that the generated power does not compromise the safety of either the people on the farm, other coop customers, or the power company line crew who may need to work on the electric system that is connected to the farm.

This is not to discourage any operations who have the capacity or interest in providing renewable energy, but to help find the answers to their questions about how to do it. An interested farm should contact their electric coop or their electric distribution company to visit with electrical engineers who work in the area of electric generation and transmission for more precise details of the requirements. Either Don Leis, Senior Power Deliver Engineer with Buckeye Power (614-846-5757) or Richard Hiatt, with the Rural Electricity Resource Council in Wilmington (937-383-0001) may be able to help those who are exploring the idea of methane production and electric generation.

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