BioCycle October 2005, Vol. 46, No. 10, p. 56
Anaerobic digesters can help agriculture coexist with increasingly urbanized areas, and what a county is doing to make that happen.

ON SEPTEMBER 9, 2005, King County, Washington Executive Ron Sims wrote a letter to his councilmembers outlining a plan to help dairy farmers in the Enumclaw Plateau stay economically viable and protect the region’s water by collecting manure and turning it into electricity. Wrote Sims:
“During the past 20 years, half the dairy farmers have left King County. We face a fundamental question about whether our dairy farms in particular, and agriculture generally, can continue to coexist in increasingly urbanized areas. This year alone, we have seen another two dairy farmers discontinue operations. Today there are only 28 operating dairy farms remaining on the Enumclaw Plateau. Since most of these dairy farms are part of the Farmland Preservation Program, the best use of this land is an active agriculture operation.”
Sims stresses that there are potentially numerous benefits to a manure management system that uses anaerobic digestion technology including: Support Enumclaw Plateau family farm viability; Preserve open space and strengthen growth management; Reduce or eliminate nutrient and pathogen discharge into the White and Green Rivers and their tributaries; Minimize or eliminate odor; Reduce solid waste; Produce clean renewable energy; Produce additional greenhouse gas emission reductions; Produce an environmentally-beneficial nationally-certified organic fertilizer from residual solids; Streamline regulatory management of effluents on farms by collecting manure and centralizing processing; and Increase tax revenues in Enumclaw and King County.
Two years ago, the Department of Natural Resources and Parks completed a feasibility study for anaerobic digesters on the Enumclaw Plateau. After continued due-diligence review of the study and extensive meetings with the dairy farmers, King County issued a Request for Qualifications for developers, and followed with a Request for Proposals.
“After an extensive process,” writes Sims, “I am now prepared to announce the development team with whom we will pursue a potential project.” The team, led by Energy Northwest, a leading energy provider to Washington State public utilities and municipalities, has assembled an impressive list of experts who can address the unique situation for our Enumclaw dairy farmers. The team members include:
o DariTech – a Western Washington company that is the leading provider of equipment and custom products for the dairy community;
o Biothane – an international company that is a leading provider of industrial biological wastewater treatment systems; and
o RCM Digesters – developer of anaerobic digesters for cow manure. (RCM was recently purchased by Biothane.)
“The Enumclaw project faces two unique challenges. First, we will have to provide a collection system for the farms rather than build 28 different anaerobic digester systems. Most modern day facilities are built on large corporate farms where they face no transportation costs of hauling manure. Second, and more importantly, farmers have made it clear that any project that is built must reduce nutrients from their pastures in order to allow them to expand their operations or to comply with future state and federal water quality regulations. With these additional obstacles to overcome, we have put a premium on securing a team with the most experience. The team we have selected is best suited to accomplish this task.”
“The first task of Energy Northwest is to meet with Enumclaw dairy farmers to scope what type of project is best suited to meet their needs. It is likely the team and the farmers will start with a smaller system that has the potential for expansion and replication. We hope to identify which farms will participate in this initial phase, where the system will be located, and what design is most appropriate. Once we reach these thresholds, King County will assist with siting, permitting and raising the necessary capital to build the system.”
According to Doug Howell, project manager in the King County Department of Natural Resources and Parks, the challenge is to reduce nutrients. The Enumclaw Plateau has a high water table that requires dairy farmers to store all their manure in lagoons for six months of the rainy winter season. The Washington State Department of Agriculture likely will not allow more lagoons to be built, which may prevent dairy farmers from expanding their operations. In addition, future water quality regulations may drive King County farmers out of business or out of the county. Therefore the dairy farmers are unlikely to participate in a project unless significant reduction of nutrients can be achieved, specifically nitrogen and phosphorous.
While anaerobic digesters do little to reduce nutrients, the dairy farmers, King County, the local Conservation District and Natural Resources Conservation Service believe that digesters probably make the most sense. “Once you have to process manure to reduce nutrients, you may need to maximize the valued-added products from manure to justify investments,” says Howell. “Digesters provide methane for energy and more marketable residual solids. In addition, digesters reduce odor, a benefit that is becoming increasingly more valuable with the ever-expanding suburbanization of the Enumclaw Plateau. The combination of digester attributes is appealing.”
King County hopes to maximize the talent of the Energy Northwest team and the R&D on nutrient reduction from around the country to help achieve the farmers’ priority. Following the plan outlined by King County Executive Sims, it would appear that the centralized digester is closer to reality – and construction.