DIGESTER TANKS AND WINDROWS CREATE WATTS AND COMPOST

BioCycle October 2003, Vol. 44, No. 10, p. 36

Oregon's Port of Tillamook Bay uses digesters, generators and turners to sell electricity to its local utility and organic fertilizer to the nursery industry.

Laura Swanson

SEPTEMBER 16, 2003 - The manure digester tanks at the Port of Tillamook Bay's in Tillamook, Oregon are full. After 30 days, by mid-October, the over one million gallons of liquid manure should be “up to temperature,” says Port Manager Jack Crider. “We'll attach the gas bags and begin generating power. It's been over 14 years in development. There have been lots of hoops and at times, it's been a logistics nightmare,” adds Crider. “From funding this as a Public Works Project, to getting all the materials, and fully engineering the conversion process of taking in manure to generating electricity. It's like a giant erector set. There have been challenges every step of the way, and there's a lot to the biochemical process involved with the digester's start-up.” They started filling the digester tanks September 10th, and the Port is in final negotiations with the local electric utility, Tillamook Public Utility District (PUD), to put the power generated by the digester directly on the grid.
The $2.5 million dairy manure digester, and accompanying $1.5 million compost facility are being built on part of the Port of Tillamook Bay (POTB) property that was the former Tillamook U.S. Naval Station. Constructed in 1943, the port was home to one of the blimp squadrons that patrolled the Pacific Coast during World War II. The central structures were two hangars measuring 1,072 feet long, 296 feet wide and 192 feet tall, the largest clearspan wooden buildings in the world. There were originally two hangars, one was destroyed by fire in 1992, the other existing hangar houses the Tillamook Aviation Museum. “For the construction of the digester and composting facilities, we are utilizing the concrete slabs and support pillars from the burned hangar,” notes Crider.
As part of the digester system, raw liquid parlor manure is trucked in from surrounding farms, and pumped into one of four 400,000 gallon covered tanks. The facility has a storage capacity of 1.6 million gallons of liquid manure. The processor will handle 20,000 gallons per tank each day. There will be 80,000 gallons of manure in, 80,000 gallons of liquid fertilizer out. “The digester is like a giant heat exchanger,” says Crider. The liquid moves through the processor at 100 degree temperatures, and the gases (60 percent methane, 40 percent carbon dioxide) are collected in bags for fuel. The digester will be equipped with four 200 kilowatt Gen-Sets to burn the methane gas to generate electricity that will be sold to Tillamook PUD for green power.
Then the liquid is put through a screw press to remove all the solids. This dry material, known as digested fiber, is a component used in potting soil mixes, particularly for rooftop gardens, that will be utilized by Pro-Gro Mixes of Sherwood, Oregon, part owners and operators of the adjacent composting facility. The remaining liquid, sterilized and odor free, is returned to the dairy farmers for field spreading. The no-maintenance process efficiently produces fuel, fiber and fertilizer.
At full capacity, the digester will handle the waste from 4,000 cows, taking in 600,000 gallons of manure each week from 20 dairies. “We're guinea pigs,” said Crider. “This is the first time a facility's electric power will go directly on the grid.” The digester will produce 160,000 cubic feet per day of biogas, producing 5 million kilowatt hours per year to the power grid - enough electricity for 350 homes. Power used by the digester process will be supplied by the biogas generation system, and additional power will go to Tillamook PUD.
“We toured facilities back East, talking to operators and dairymen as we finalized the design for our facility,” Crider recalls. “There is a visitors center that will provide details about the digester technology, manure management and more. This will be an educational tool.”
The community liquid digester is the first of its kind in the country and the first large-scale dairy manure digester in the Northwest. The Methane Energy and Agricultural Development (MEAD) project enables dairy farmers to increase dairy herd production without increasing air odor and water pollution from animal waste. The Tillamook County dairy cow population of 30,000 has outgrown the human population of 24,000. The MEAD project goals are to provide needed services to farmers; to develop local, renewable electrical generation; to enhance environmental quality; and to generate income for the community.
The two businesses - the digester and compost facilities - will provide 13 family wage jobs. Revenues from this first community digester will be used to finance more digesters centrally located around the county. Centralized units, costing an estimated $1 million each, will save trucking costs.
“The digester is coming on-line just before the rainy season, which is perfect timing. We'll start with the waste from 1,000 cows adding more gradually, until we reach the facility capacity of 4,000 cows,” sums up Crider. “After the 14 years of proposals and planning, actual operation is a huge relief. It's really amazing that we are all so excited about tanks full of bubbling liquid manure.”

OPERATIONS AT THE COMPOSTING FACILITY
One of the top dairy counties on the West Coast with a seemingly endless supply of both manure and woody debris from nearby mills, Tillamook County, Oregon has a win-win location for a composting facility. For Pro-Gro Mixes & Materials of nearby Sherwood, this operation it now owns in partnership with six dairymen is ideal. “We determined that market demand by the nursery and landscape industries in the Pacific Northwest for a quality, consistent compost product was going to increase,” explains Pro-Gro president Dave Andrews, “so we have been working to establish our own facility to have the ultimate control of the supply and quality.”
Adjacent to the Port of Tillamook Bay's manure digester that processes the liquid wastes generated at surrounding dairy farms, the facility - called Compost, Inc. - can handle a large volume of feedstocks. The $2 million site has a covered area 560 feet by 285 feet, and a storage capacity of over 17,000 cubic yards. It uses manure solids and animal bedding and wood residuals to produce compost.
“We regularly send samples of our compost for testing and analysis. All our test results have been clean, and show high nutrient levels,” said Russ Halvorsen, on-site manager. This partnership between the dairymen, led by Don Averill Farms, and Pro-Gro Mixes & Materials will market and distribute the finished compost products which are key components in potting and nursery soil mixes.
As the materials (manure and wood residuals) reach the facility, they are mixed with appropriate levels of carbon materials; minor amounts of finished compost are added to enhance the process with other amendments as required. “The composting takes from 90 to 120 days,” says Halvorsen. “We test the temperatures of each row every two days and have average temperatures of 134 degrees. To keep the supply consistent, we track incoming loads. When the temperatures reach 150 degrees, we turn them again,” he adds. Windrows are up to ten feet high and turned with a Frontier machine. An air flow system under the piles is planned.

The first loads of finished compost product from Compost Inc.'s Tillamook facility were trucked out by Pro-Gro in early May. “In the first phase, we are shipping out 5,000 cubic yards, about 100 truckloads every month,” states Andrews, “And we anticipate doubling that production during the drier summer months.
The facility will also add compost drying and bagging equipment. Currently, the finished compost is being sold wholesale at bulk rates, $3 to $4 per yard; bagged compost for the retail market has a return of $15 to $20 per yard.
For more information about the Port of Tillamook Bay's digester and compost facility, contact Jack Crider at jcrider@potb.org.

Copyright 2003, The JG Press, Inc.