Anaerobic Digesters Move Into Oregon

From BioCycle
Journal of Composting &Organics Recycling
May 2001, Page 34

SUSTAINABLE GREEN POWER
ANAEROBIC DIGESTERS MOVE INTO OREGON
During the past six months, construction has begun at three digester sites in Oregon, with six to eight more in the planning stages.
Will Charlton

WHAT are the reasons for the increasing interest in anaerobic digestion that is building in the state of Oregon? Can it be linked to Governor Kitzhaber’s Sustainability Order? Is it rising electricity prices? Is it the need for second incomes for dairies ... or the escalating manure handling issues? Are there connections to the Save the Salmon efforts? Or is it just the right timing?

Over the past ten years, digesters have been evaluated as alternative electricity sources in the Pacific Northwest — especially in Oregon. In 1994, the Craven Farm digester started using a plug flow system for around 1,000 cows. No longer operational, this had been the only digester in Oregon — that is until now.

In the last six months, construction has begun at three digester sites in Oregon with anywhere from six to eight more digesters in the planning stages for the next two to three years. The biggest players in the anaerobic digester scene in Oregon have been Portland General Electric and the Port of Tillamook Bay.

Portland General Electric (PGE, not to be confused with PG & E in California) has taken an aggressive approach to setting up digesters in Oregon. Where traditionally the initial start-up and maintenance costs proved to be more than farmers were willing to undertake, PGE has stepped up and is willing to take on the challenge.

PGE set about looking for “Green Power;” they talked with several people and organizations before arriving at anaerobic digestion as a win-win solution. Jeff Cole, Biogas manager for PGE, began discussing with the Oregon Dairy Farmers Association (ODFA) about finding a pilot location for their first digester. Jim Krahn of ODFA and Cole worked together to establish a home for the first PGE digester. They selected the Cal-Gon Dairy, which is a relatively small dairy with 500 cows. PGE worked out the arrangements so that the farmer, Bernie Faber, did not have any start-up or operational costs. This first digester is the pilot project for PGE, and they will be able to determine economic feasibility of operating on farms.

The Cal-Gon digester will handle 500 animals, and will likely be the smallest of the PGE digesters. This digester will process 12 percent solids and utilize a “Complete Mix” digester system. The tank foundation and walls are complete; currently they are forming the tank lid and starting the piping. Cole anticipates that this digester should begin loading manure in May and generating methane gas in June. The digester at the Cal-Gon farm will operate at mesophillic temperatures to start, but will have the capability to operate at thermophilic temperatures.

LARGER PROJECTS PLANNED

PGE’s other planned facility in Boardman, Oregon at Threemile Farms LLC will be at the extreme other end of the size spectrum. This digester will likely be PGE’s largest with a handling capacity of 22,000 animals. This farm will have more liquid and less solids in their manure (six percent solids). Currently, this project has had some site preparation completed and is going through the funding process. Cole believes that this site should be completely operational and producing methane by July of 2002. By that same time, PGE anticipates having five to six digesters in construction. Unlike the Cal-Gon digester, the Boardman digester will operate within thermophilic temperatures.

Of the five to six digesters that PGE might develop over the next couple of years, they will all range between 1,000 and 3,000 animals each. PGE is also looking forward to developing a relationship with Oregon State University (OSU) on research projects in regards to field applications and other various uses for the fiber.

Once the liquid manure is inside the digesters, it will be processed anaerobically and then separated into solids and liquids after it leaves the digester vessel. The digestion process kills off much of the Salmonella and E-coli bacteria and reduces the nitrogen content (to a lesser degree), thereby making life for the farmer easier as the main water pollutant is pathogens, with nitrogen currently being the second concern. The liquids will be piped into liquid containment tanks and sprayed as needed as a liquid fertilizer onto the fields. The solids will then be taken to the composting site managed by Pro-Gro Mixes, Inc. (See page 51 of February, 2001 BioCycle, “Targeting Composted Manure For Nursery Mixes.”

PORT OF TILLAMOOK PROJECT

The other significant digester in Oregon is located 15 miles north of where the Craven Farm Digester was operating — a few miles south of the city of Tillamook, off Highway 101. The Port of Tillamook Bay received a $1 million special appropriation from the U.S. Department of Energy to set up a digester. This first digester’s capacity will be 2,000 to 3,000 cows. They are currently in the contracting stage of development and RFPs have been issued for a consultant. With some site preparation underway, construction will begin in July. According to Jack Crider, the Port of Tillamook Bay General Manager, the plan is to start accepting manure in early November and begin producing methane by December. The specific system utilized is to be determined. Crider is anticipating that six nearby dairies will participate in this initial digester. Within the next two years, the Port of Tillamook Bay is anticipating three more digesters — all with about the same capacity, strategically placed within Tillamook County where local dairies can participate.

Here again, the liquids and solids are separated. The difference though is that the Port of Tillamook facility is a centrally located facility with liquids hauled in daily to fuel the digester and liquids hauled out daily from the digested materials. The liquids go back to the farmer to apply on the farms, and in some cases could be used to add liquid to Pro-Gro Mixes composting facility, also located on the Port of Tillamook Bay. The solids will go to Pro-Gro.

COMPOSTING OPERATION

Once the digested fiber (residual solids after digestion) is delivered to a Pro-Gro composting facility, it will be aerated to allow beneficial microbial populations to return. This also allows the materials to drop to 40 percent moisture content, a level that is preferred for mixing machines to properly process. The composted fiber will then be mixed with other standard potting soil blends for the nursery and landscape industries. Pro-Gro had been purchasing fiber from the Craven Farm, and will be purchasing the fiber from the newer facilities for blending with other feedstocks. Digested fiber is a highly desirable component for rooftop garden mixes and for other landscape applications.

Within the Northwest there are others talking about producing green energy by digesting manure. They include two companies in Idaho; three to four in Washington; and two to four more in Oregon that are in the feasibility and risk assessment stages.

Will Charlton is the Compost Resource Specialist with Pro-Gro Mixes, Inc., based in Tillamook, Oregon.

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