Anaerobic digester operators describe benefits, challenges
By STEVE BROWN
OLYMPIA -- With four years of experience behind them, owners of an anaerobic digester in Snohomish County, Wash., say the operation has brought many benefits -- and some challenges.
Dairy farmer Andy Werkoven, systems manager for the nonprofit partnership Qualco Energy, told Thurston County citizens interested in building a similar operation that the digester is "like a mechanical rumen in a lot of ways."
Just as he learned to adjust his cows' feed, he has learned to change the recipe of what goes into the digester.
But the structure was not built for the mix of inputs it now handles. Qualco president Daryl Williams said it was designed only for cow manure, but the addition of trap grease, expired beer and preconsumer food waste has complicated the operation.
One thing treasurer Dale Reiner said Qualco would do differently is the timing of the startup. Before the system could work, its 1,452,000-gallon digester had to be brought up to 100 degrees, not a quick task in December.
And the system is not cheap. The $4 million project was funded by a 13-year loan through a Bank of America Clean Energy Bond and a USDA grant of $500,000.
Despite the challenges, Reiner said, the system is doing what it's supposed to do, keeping the manure and the other waste products out of landfills and sewers and converting them into useful products: electricity, high-quality compost and liquid effluent ready to apply to the dairy's fields.
"We take the slop in life and make the best of it. This system thrives on slop," Werkhoven said.
The best benefit, Williams said, is the relationships the project has developed. It has brought farmers, environmentalists and Native Americans together.
The nearby Snohomish River watershed had to be protected as salmon habitat, and for the Tulalip Tribes, "the river is our lifeblood," said Williams, who is also the tribes' environmental liaison.
Reiner said the idea of raising cattle on one side of the high-water mark and protecting salmon on the other side became the basis for the close relationship.
The panel discussion in Olympia is just the initial conversation for Thurston County interests, said Lucas Patzek, director of the county Washington State University Extension office.
Sandra Romero, Thurston County commissioner, said the meeting left her "more energized than ever. If Snohomish County can do it, we can do it."