| Digester helps dairy with odor, nutrient management |
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Bernie Faber began operating Oregon’s first methane digester in cooperation with Portland General Electric in 2001. His West Salem operation, Cal-Gon Dairy, is now a popular stop for other dairy operators, organizations, and agencies wanting to learn about the technology and Faber’s first-hand experience.
Faber explains that the system was designed to process manure from 500 cows. “PGE was looking for a medium-sized dairy to develop a digester as a demonstration project,” he says. “We’re currently milking about 300 animals.” The digester’s current output is between 30 to 40 kilowatts.
To begin the digestion process, manure is scraped from the barns into a concrete tank, then pumped into the digester. Bacteria digest the manure, producing methane that collects in a tank. The methane fuels a gen-set that feeds electricity into the power grid. A recapturing system takes the heat produced by the engine and transports it back into the digester, helping to maintain high temperatures to support the digestion process.
After manure leaves the digester, liquids are separated and piped into a manure lagoon. Solids are stored for a few days, then collected by a company that composts them along with yard waste. “Solids come out of the digester at about 90 to 100 degrees,” Bernie Faber explains. “So they help speed up the composting of the yard materials.”
Faber reports that he used to get a lot of questions from other dairy operators about the payback time frame on the methane digester at his dairy, or whether he would still build a digester if he could do it all over again.
“People don’t ask me that anymore,” he says. “Now they ask, ‘How does this help with odor?’ or ‘How does this help with environmental issues?”
Odor from dairy manure is an issue in West Salem, with a mixture of agricultural and rural residential neighbors nearby. Faber reports the digester has successfully reduced odor and has also helped the dairy achieve more balanced nutrient applications to their cropland. Before the digester was installed, both solid manure, which contains most of the phosphorus, and liquid manure were spread onto cropland. Excess phosphorus, which can accumulate in the soil when manure is applied to provide enough nitrogen for crop needs, had been a concern for the Fabers.
With the digestion, separation, and export system the dairy now has in place, the phosphorus content in the manure applied to cropland is now greatly reduced. Now, most of the solids are separated out after the digestion process and exported to the composting company.
The digester was a significant investment for both Faber and PGE, and maintenance costs are also considerable. “If you’re not interested in digesters, or if you want a payback of five to seven years, they’re probably not for you,” Bernie Faber explains. “But it’s helped with the challenges we were facing with odor and the land base for manure application. If we weren’t able to export the solids from the digester, we would be faced with purchasing at least another 100 acres to accommodate the phosphorus in the manure.”
Faber encourages other dairy operators considering digesters to make sure they get assistance from qualified engineers, and to do extensive research and evaluation to make sure a digester is right for them. He recently had some dairy operators visit from New York who also operate in a mixed-use area and are facing some of the same challenges with land base. “I told them, ‘You’re doing the right thing by visiting other operations. Do your homework and figure out if a digester is a good fit for your operation,’” he says.
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