Each day, the 17,000 dairy cows at Threemile Canyon Farms east of the Columbia River Gorge produce a staggering 120 pounds each of waste, routed through pipes and concrete sluices to manure lagoons that release vast amounts of methane, a potent greenhouse gas.
Today, the Boardman farm, the utility Northwest Natural Gas Co., and the Bonneville Environmental Foundation announced Threemile's biggest step yet to addressing that problem: a pollution-reducing manure "digester" that would trap the methane for use as fuel on the dairy farm, one of the nation's largest.
The $1 million investment will be split between the foundation and the stockholders of NW Natural, which can benefit from state tax credits attached to the project. The operating costs, estimated at $20,000 a year, will be covered by the 6,300 NW Natural customers who have signed up to pay extra on their monthly bill to fund green projects.
The digester, essentially a huge, tightly covered lagoon, is far from a complete solution. When it starts up in March, it will process a fraction of Threemile's manure output, handling waste from 1,000 to 1,400 cows. And it won't address ammonia emissions that scientists say contribute to haze in the gorge. Unlike California, Oregon's large dairies are exempt from air quality regulations.
But if it works as expected, the digester will cut odors from the dairy and keep the equivalent of 1,500 tons a year of carbon dioxide out of the air -- roughly the emissions generated from 400 homes using natural gas, NW Natural says. The digesters could multiply at Threemile and elsewhere if a new design, billed as cheaper yet more efficient, pans out.
"If this works the way we think it's going to work, it's a low-cost solution for dairies of any size, and it will plug right into the current (manure) collection system," said Marty Myers, Threemile's general manager.
Digesters aren't new. The U.S. Environmental Protection Agency counted 114 of them at commercial livestock operations in April, including five in Oregon and three in Washington.
But the digesters are typically either inefficient covered lagoons that don't do as much for the environment, or expensive systems of concrete and metal tanks that cost too much, said Bill Eddie, a director with the Portland-based environmental foundation.
A new design, from the Boise-based engineering firm J-U-B Engineers Inc., will be used at Threemile. It will incorporate 35,000 used tires as "fixed media" to help promote the anaerobic bacteria that convert manure to methane. And it will come in standardized modules, allowing for easy expansion.
The Threemile lagoon will be the first large-scale test of that design, Eddie said. It's also the first green project that NW Natural year-old "Smart Energy" program customers will invest in. An independent third party auditor will verify the project's greenhouse gas reductions.
If the pilot project works, the low-cost design and the heavily subsidized financing could make it popular with farmers. Oregon has about 85 dairies with 500 cows or more, and they're under increasing pressure to reduce emissions and odor.
"We wouldn't be doing this," Eddie said, "if we didn't think the design had potential for broad applications."
-- Scott Learn; email@example.com