Biomass digester to use dairy waste

By Ryan C. Christiansen
Web exclusive posted July 15, 2008 at 12:16 p.m. CST

Several years after a biomass digester was first proposed to help consume waste from local dairy operations and prevent runoff into local salmon streams, work crews have begun building a plant in the Tualco Valley located in the Skykomish River and Snoqualmie River floodplains south of Monroe, Wash. The digester will be complete and ready to accept manure feedstock by the end of October.

If all goes as planned, the facility's generators will begin producing electricity from the methane gas in January, which will be sold to the Snohomish County Public Utility District, according to Dale Reiner, representative for Qualco Energy Corp. Qualco is a non-profit organization that includes representatives from the Sno/Sky Agricultural Alliance, a dairy farmers' group; Quilceda Power, a subsidiary of the Tulalip Tribes; and the Northwest Chinook Recovery, a nonprofit organization founded in 1997 to preserve, restore, and enhance salmon habitat in the Puget Sound region.

Reducing groundwater and salmon stream pollution from dairy operations is one of the primary reasons the digester is being built, Reiner said. "This certainly played a factor in the formation of this whole organization," he said, noting that the Tulalip Tribes have a key interest in preserving the salmon population. The dairy farmers will benefit too, he added. "This project will allow participating dairies to grow their herds to the size that best fits their business plan, management style, and future goals, without being restricted by the number of cows allowed on a per-acre basis."

Three dairy farmers collecting manure from approximately 1,600 cows will supply the feedstock for the digester, which will take six weeks to fill and rise to the required temperature for digestion, Reiner said. The plant's generators will produce 450 kilowatts of power, enough to power approximately 300 homes, said Neil Neroutsos, a spokesman for the Snohomish County Public Utility District. He said the district and Qualco Energy continue to negotiate the power purchase agreement.

The county's public utility district became involved in the project in 2004, soon after the project was initially proposed, Neroutsos said. "In the past several years, we have provided technical support to assist the developers," he said, "including how the energy output would be integrated into the existing electrical system.

"Like most power projects there are typically some technical challenges," he said. "However, we look at the project as an opportunity to educate the public about how this power source works, conduct educational tours, and increase overall understanding of biogas generation."

Neroutsos said the biogas digester will help the public utility district meet a portion of the utility's renewable portfolio standards requirements. The utility also has two biomass facilities that use wood waste to produce electricity, including a Kimberly-Clark paper pulp mill in Everett, Wash., and the Hampton Affiliates lumber mill in Darrington, Wash., as well as a garbage landfill gas project in eastern Washington. The company is also looking at the viability of using tidal and geothermal energy to produce electricity.

The biomass digester in Monroe, Wash., will have enough capacity to digest feedstock from 2,200 cows, Reiner said. The digester is being built on the 277-acre site of the former Washington State Reformatory Dairy Farm, which for 72 years was a prison farm, according to the Quilceda Power Web site. The farm closed in February 2001.