Montana's First Methane Digester

(from the Ravalli Republic)  Long considered a family farm on the cutting edge of technology, the Huls dairy farm in Corvallis kept up with appearances this year by installing the state’s first methane digester.

The two 31,000-pound tanks will generate 50 kilowatts of power continuously, creating energy from cow manure. The methane gas from that manure is the equivalent of the Hulses having a natural gas well on their property. Not only will they be able to power their entire state-of-the-art dairy farm, they’ll be selling energy back to the grid.

The methane is digested via an anaerobic process. Bacteria digests the effluent so actively that, from the top of the digester looking in, “it looks like a boiling pot,” Dan Huls said.

First, manure from the 350-cow barn is pumped into the digester tanks. Bacteria inside the tanks digests the solids from the slurry. Forty to 50 percent of the solids are digested, and the other half is separated before the effluent goes to the holding pond with a solid separator.

Gray water from the tank is sent to a near million-gallon holding pond that gives Huls more than 180 days of storage. That water is then used for irrigation.

Overall, the project will end up costing nearly $1 million, a great deal of which was paid for by grant funding from the Natural Resources Conservation Service, the Montana Community Development Corporation and the Ravalli County Economic Development Authority. The federal money from the NRCS comes after the project has been completed. MCDC and the Ravalli County EDA helped with funding during the interim.

According to Kevin Pack, owner of Andigen, which builds the tanks, estimated that Huls will have his project paid back in less than three years.

The methane digester is a prime example of sustainable energy. The Hulses will be selling energy back to the grid as well as carbon credits for methane. Plus, with 350 well-fed cows, they have a never-ending supply of fuel.

The digesters were created based on research done at Utah State University.