University of Wisconsin Extension agent Vance Haugen has long been fascinated with the potential of manure digesters, and long been frustrated that they were only considered appropriate for giant farms. Manure, he figured, is manure, and bugs are bugs. Why not try a small-time approach using cheap components instead of giant tanks with fancy valves, pumps and motors?
Last year, Haugen visited Zambia to work on methane digesters for subsistence farmers who typically have only a cow or two. To them, methane was not a source of fuel for electric generators but for cooking. Using 55-gallon drums, Haugen helped create tiny methane generators that could be controlled with a lot of hand labor -- something Zambia has in ample supply.
“The digesters made economic sense because they do not have a cheap, reliable energy source,” says Haugen. “We were trying to reduce deforestation, and it's just dangerous to go out in the bush to get trees to make charcoal.”
Because methane is expensive to compress and store, many U.S. projects have focused on burning the gas to make electricity, but losses in the engine and the generator reduce the overall efficiency. When methane is burned for heat, Haugen says, "It's almost 90 percent efficient."
Big farmers get much of the attention, and are the only market for expensive methane-makers, but Wisconsin has 13,000 dairy farms with fewer than 200 cows, Haugen says. "It's a frustration, we've got a lot of economically viable farmers with 100 cows, they are still making money."
And, we might, add, manure.
Third world coming home?
In an effort to develop a low-cost methane digester for the many small farms in Wisconsin, Haugen looked to a Southeast Asian design, which uses giant plastic tubes and plastic plumbing to produce biogas systems. The systems that Haugen envisions would shut down during the cold winter, but dairy farms need energy to heat water for washing cows and equipment all year long.
Manure-to-methane could provide some energy, reduce the environmental impact, save a little money, Haugen says.
Haugen is currently soliciting farmers to try some trench warfare against the inevitable waste products of dairy farming.
Terry Devitt, editor; Nathan Hebert, project assistant; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive