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Art Thelen of Wild Rose Dairy in La Farge is a pioneer in methane digester technology, which uses methane gas from animal waste as fuel.
“I used to live in the house just down the road, and I would walk to the farm almost every morning,” Thelen said. “I would pass the manure lagoon, and as the sun came up. I would see these big bubbles forming on the top … and as the sun would hit them, they would burst and, poof, that was the methane gas just going up into the air.”
Capturing that gas is the job of methane digesters.
The basic principal is to introduce bacteria into a manure-holding tank that is constantly circulating. The circulation keeps solids suspended and allows the bacteria to break down the waste.
The other ingredients needed to complete the process are heat and the introduction of a “substrate” of organic material that bacteria can feed on to complete the process. Substrates are organic waste materials, such as grease and restaurant waste, that normally would be hauled to a landfill. Thelen said about three semi-loads of substrate are added to the facility each week.
As the digester breaks down the waste, the methane gas is collected in the top of the tank and siphoned off to power a generator. Wild Rose farm has an about 800 kilowatt generator, big enough to power about 650 homes.
One advantage to the system is the end product still can be used as crop fertilizer. In fact, this material is better because it has been “cooked,” killing any weed seeds that might be lurking within.
The facility has been in operation for about a year and, for the most part, has worked well, Thelen said.
“We have some small issues but nothing major,” Thelen said. “Just like with anything else, we have had to do some tinkering.”
John McWilliams, a resource planner for Dairyland Power Cooperative, said Dairyland has helped construct three such facilities so far.
The other two digester units are near Elk Mound and at Norwiss Farms near Rice Lake. Dairyland has long-range plans to develop up to 20 such facilities.
“We would eventually like to produce about 20 to 30 megawatts using this technology,” McWilliams said. That’s enough energy to power about 20,000 homes.
For Wild Rose Dairy, the decision to construct the digester was a good one.
“If we could put all of the animals in the right places and collect all of the waste they produce across the country, we could produce a lot of energy,” Thelen said.
Tim Hundt is a reporter for the Vernon County Broadcaster.
