January 30, 2006 | General

Integrated Approach To Digesters in Washington State

BioCycle January 2006, Vol. 47, No. 1, p. 51
University team works with local farmers, designers and others to develop systems, improve process results to validate digester use.

A TEAM of Washington State University researchers and extension specialists is developing an integrated research and demonstration program on anaerobic digestion of animal manure. The WSU team has forged a solid, collaborative relationship with regional farmers, engineering and consulting firms, and digester designers, fabricators, and marketers.
Ongoing projects and emphases include: 1) Research and development into novel digester components and systems aimed at reducing fluid retention time, reactor volume, and capital costs while simultaneously providing for new coproducts; 2) Monitoring and evaluation of existing commercial and pilot-scale digesters and digestion products to provide both technical support and extension material for producers in search of valid, independent, third-party digester data; 3) Mathematical modeling of biological, chemical and physical systems within the digestion process for the purpose of both further understanding the basic science and using that understanding for reactor design and process optimization; 4) Development of coproducts for improved revenue sales, including development of processes for ammonia stripping/adsorption, phosphorous precipitation, and peat moss quality fiber; 5) Evaluation of anaerobic digestion and other on-farm manure management strategies as a means for improved air and water quality health as well as a “source to sink” for greenhouse gases; and 6) Demonstration of existing digester technology at a commercial dairy.
The research projects encompass activities that range from bench-scale laboratory studies in a specially designed anaerobic digestion “hot room” to pilot-scale and field-scale studies at the WSU Dairy Center and Prosser Agriculture Station to commercial studies at the Vander Haak farm in Lynden, Washington. Funding for the various projects derive from such sources as: the Paul G. Allen Family Foundation, a USDA-NRCS Conservation Innovation Grant, USDA-SBIR, the Washington Technology Center, the Washington Department of Ecology, and the Andgar Corporation.
Deliverables and activities to date include construction and ongoing evaluation of a GHD Designed digester at the Vander Haak Dairy, construction and ongoing study of a 25-cow equivalent dairy manure digester at the WSU Dairy Center, sponsorship of several digester technology demonstrations, workshops and forums held in the region, development of several patent-pending processes for production of high-value coproducts, and on-going field and laboratory studies within crop and soil sciences, engineering and economics.
A report on this research and commercial application on anaerobic digesters will be presented at the BioCycle West Coast Conference in Portland, Oregon March 20-22, 2006. This data was summarized by Craig Frear and Chad Kruger of Washington State University, Darryl Vander Haak, dairy owner, and Bryan Van Loo of the Andgar Corporation.
LAST SPRING, dairy farmer Darryl Vander Haak began operating the first anaerobic digester in Washington to convert manure into renewable energy. Three farms are supplying manure from about 1,000 cows with a pipeline from Vander Haak’s other dairy two miles away delivering feedstock plus another neighboring dairy bringing in manure by truck. Puget Sound Energy is purchasing the methane for electricity as part of its Green Power program where customers pay an extra $4/month to support alternative energy. More than 1,400 Whatcom County residents have signed up as has Western Washington-University.
The Andgar Corporation based in Ferndale built the $1.2 million digester. Marketable by-products besides the power include the solids (or fiber) which are sold as compost or bedding, and the liquid by-product which is rich in phosphorus and nitrogen can be used for fertilizer. In addition, the process reduces greenhouse gas emissions along with odors, while protecting water quality. “It’s been a team effort,” says Vander Haak of the partnerships with public and private organizations to construct the digester. Original financial support came from the USDA’s Rural Development grant program.

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