Cow power

RUPERT, IDAHO -- Square holding pens and three long barns house nearly 6,400 cows at the Whitesides Dairy. Black-and-white heifers mill around in the pens, sticking their heads between bars to reach a row of feed. From inside the barns comes Latino music, the mechanical hum of milking machinery, and constant mooing as cows are herded into the milking parlor.

In most respects, Whitesides Dairy resembles the other 334 registered dairies scattered across southern Idaho’s Magic Valley, cow capital of the fourth-largest milk-producing state in the country. But the aluminum building at the far end of the farm holds something different: 10 vertical steel tanks, each one a looming 35 feet tall and 13 feet across. Along the top of the building runs a tangle of gleaming pipes.

This unusual machinery has nothing to do with milking cows; it’s an anaerobic digester. Typically, dairy farms flush gargantuan amounts of manure from their barns and pens into nearby lagoons. As bacteria break down the manure, methane and carbon dioxide are released into the atmosphere. A digester captures those gases so that they can be converted into energy — electricity or heat.

Across the country, dairy farmers are installing digesters to curb emissions and odors, and to generate power. Idaho has lagged far behind in the effort, thanks to the state’s low energy prices and a lack of subsidies. But at Whitesides Dairy, Intrepid Technology and Resources Inc. is working on an innovative project to create and sell pipeline-quality natural gas. If the effort succeeds, it could pave the way for Idaho’s dairy country to turn cow poop into cash.

Interest in digesters first emerged during the energy crisis of the mid-’70s, but the early machines were plagued by operational difficulties. Lately, the push to diversify energy sources has brought digesters — which have undergone technological improvements — back into vogue. And with livestock waste accounting for 8 percent of human-related methane emissions in the United States, the digesters have the potential to help curb dairy farms’ contribution to global warming.

There are many types of digesters, but all work on the same concept. A digester captures the methane that is released by bacteria breaking down manure. In most cases, the methane is used to run a modified internal combustion engine, which generates electricity. This electricity can be used on the farm, with excess sold into the grid. The process also kills pathogens in manure, turning it into a more environmentally friendly fertilizer.

Digesters are catching on in dairy states around the country: Wisconsin boasts 21 and California has 18. But in Idaho, the technology has been slow to take off. A traditional digester can cost as much as 3 million dollars, and with Idaho’s relatively low power rates, the system takes years to become profitable. “The rates are just borderline in making these things economically viable,” says Greg Ledbetter, a dairy farmer with plans to begin building a digester this summer. “To say that I’m frustrated would be an understatement.”

Federal and state grants and cost-share programs often help cover the daunting capital costs for most digesters. In 2005, the U.S. Department of Agriculture Natural Resources Conservation Service awarded $450,000 to Ledbetter for his project, one of only two such subsidies for anaerobic digesters in Idaho. The funding has not been offered again because, as of now, Whitesides Diary hosts the only functioning digester, and it’s not yet on line. But Bob Bartholomew, assistant state conservationist with the Idaho NRCS, says he anticipates that when there is a viable model in Idaho, “we’ll offer the cost-share.”

That day may be getting close: Intrepid Technology and Resources Inc. recently completed the state’s first digester on the Whitesides Dairy. Four Idaho engineers took over the company six years ago. The founders saw potential in anaerobic digestion and built a prototype two-digester system in 2004. This March, the company completed eight more digesters, able to handle most of the manure from the 6,400 dairy cows on the farm.

Intrepid is stopping one step short of turning the gases into electricity. Instead, the company is adapting the technology to create natural gas. By cleaning captured methane of other products — carbon dioxide, water vapor, and hydrogen sulfide — the plant can produce pipeline-quality natural gas, garnering up to 50 percent more money than what could be made from generating electricity. “This facility will be the first natural gas well in Idaho,” says Wayne Tolman, engineering technician at Plant Operations. It will produce an estimated 270,000 cubic feet every 24 hours — enough gas to heat 1,500 homes. Intrepid has signed an agreement with Idaho Intermountain Gas, but the technology is still being adapted and tested, so the methane won’t make it into pipes until late summer.

In the meantime, Intrepid is looking at capitalizing on other markets. A post-digester process separates leftover solids from water and composts them, creating fertilizer. Emerging carbon markets also offer financial possibilities. As soon as the plant is fully operational, Intrepid will list, and sell, credits on the Chicago Climate Exchange, a voluntary U.S. carbon credit market.

Dairy farmers are excited about the potential benefits of Intrepid’s digester; the system resolves waste management issues, reduces odor, and, at the Whitesides Dairy, provides natural gas to help heat water. But farmers, agency heads and state experts remain skeptical. To date, Intrepid has yet to see any return on the investment. “They’re waiting to see if this thing takes off and flies,” says Tolman. “If it takes off and flies, it’s going to go nuts.” In the meantime, Intrepid is already well into the construction of a second digester at Westpoint Dairy in nearby Gooding County.

The writer is an HCN intern.

• Energy & Industry
• Idaho