September 21, 2010 | General

Farm Digesters Generate Revenues, Manage Odors

BioCycle September 2010, Vol. 51, No. 9, p. 41
BioCycle Energy Conference features three digester owners and operators – Farm Power Northwest, LLC, OLean Energy and Pagel’s Ponderosa. This article previews their experiences, to be shared on October 18 and 19 in Des Moines.
Dan Sullivan

FARM Power Northwest, LLC was founded in early 2007 by two brothers, Kevin and Daryl Maas, to develop, own and operate anaerobic digesters. Two years later, during construction of their first project, Farm Power began having a wider impact by joining forces with other western Washington digester owners who were struggling with regulators over codigestion of manure and food residuals. “We came in planning to codigest, joined that struggle and got the clearance,” says Kevin Maas, who, like Daryl, had studied history as an undergraduate but then pursued an MBA in sustainable business while his brother served in the Air Force.
Farm Power Rexville now operates a 750 kW mixed plug-flow digester designed for 1,500 cows on two adjacent farms. “It has been in operation since August 2009 and has produced more than 4 million kWh while also recycling thousands of tons of food waste and saving the supplying farmers nearly $100,000 in bedding costs,” says Kevin Maas. In addition to dairy manure, feedstocks coming from the community include wastes from fish, poultry and other food processing operations.
Construction began on the brothers’ second project, Farm Power Lynden, in June 2010. “It’s a 750 kW mixed plug-flow digester designed for 2,000 cows on a neighboring dairy farm,” explains Maas. “The waste heat from running the genset will also supply about half of the annual needs of a nearby 3-acre greenhouse.” Area businesses that generate food waste also profit, he says. “Those businesses benefit from a lower cost and a more flexible solution than any other method of food waste disposal.”
Construction of the 1000 kW Farm Power Rainier mixed plug-flow digester near Enumclaw, Washington, is expected to begin later this year. “This project is designed for 1,400 cows on at least four neighboring dairy farms, and it will recover about half of the nitrogen and phosphorous from the manure for export out of a sensitive watershed,” says Maas. Manure feedstock for the community digester will be both piped and trucked in. “That area has plenty of cows but not enough land,” he adds. “King County has pledged a grant to the facility. Like our previous two projects, Rainier Biogas’s other funding comes from a combination of a USDA energy grant, a USDA-guaranteed ShoreBank Pacific loan, Farm Power equity and Washington state energy program money.”
Farm Power has been working with GHD/Andgar and Washington State University to fine-tune the systems to their particular applications. “There has been a lot of trial and error,” says Maas. “We wanted to be assured that it was farmer friendly and that it worked.” All three projects were built by Andgar Corporation utilizing GHD, Inc.’s patented two-stage anaerobic digester (AD) technology.
For its first foray outside the Evergreen State, the company recently received an Oregon state energy program grant – funded with federal economic stimulus dollars – for Farm Power Tillamook, a 1,000 kW mixed plug-flow digester designed for 1,800 cows on at least three neighboring farms just outside Tillamook, Oregon, a community well-known for its dairy products. “It was a short-notice grant,” says Maas. “We had relationships with the farmers and the local utility.” Tillamook – a characteristically wet coastal Oregon town with the added moisture challenges of rivers separating farms, was already home to an older digester, he adds. “We chose an area where we could pipe from a number of nearby farms knowing the GHD system could handle [the moisture]. The intended digester for the project is designed to handle anywhere from 6 to 15 percent solids.”
Farm Power purposely seeks investors who are members of the community. “We are raising money for this project and further expansion with a Small Company Offering Registration (SCOR) open to the public, which allows us to broaden our local investor base,” Maas says, adding that the company’s roots and growth have all been without the benefit of any large institutional backers.
But it always helps to have support from local lenders. “We have convinced ShoreBank Pacific that the GHD-designed, Andgar-built digester does what we say it will do, so there is no [unknown] technology risk,” explains Maas. Potential risks of feedstock shortages are assuaged by working with multiple farms and utilizing codigestion, he adds. “If we lose a farm, we have other farms; if we lose food waste, we have a lot of manure. It makes ShoreBank comfortable that the risk is low and that we will not run out of [feedstock] before we pay off the loan.”
For the involved farmers, Maas says, the payback has “primarily been bedding up until now. In the future, it’s going to be more nutrient management. That’s getting to be a bigger issue and not one that is easily solved.” Farm Power will add a nutrient recovery component, so effluent is less potent and farmers can use more on less land. “We’re going to make sure farmers come out better off than they were before and at no cost to them,” he says. “That is the core of this – farmers put in no money, and they spend no money. They just commit to us, and we get to work.”


When Danny and Josie Kluthe decided to double their swine operation in Dodge, Nebraska to 8,000 head, they thought about what their neighbors would think, or more precisely, what they would smell. And so, in partnership with the Nebraska Public Power District (NPPD) and with the financial support of grants from USDA Rural Development and Nebraska Environmental Trust, the pioneering Midwest farming couple created OLean Energy and installed the state’s first anaerobic digester (AD) system to produce power from recovered methane. The Natural Resources Conservation Service also shared in construction costs, and NPPD assisted with the hookup to the local power grid. The cogeneration system has an 80 kW capacity and was designed by RCM, International, Inc. “We call it a manure processing system,” explains Danny Kluthe. “All the manure goes through the system and comes out practically odorless. We still have the pleasant smell of hogs, but we got rid of that hostile odor.”
Manure from the hog operation is pumped daily into an in-ground cylindrical tank fitted with an insulated flexible cover. The complete mix digester stirs and heats the waste to produce methane, which is captured and pumped into an 80 kW Caterpillar engine. “We have a heat exchanger that captures the heat of the engine and exhaust,” explains Kluthe. “It’s brought down to the digester to heat it to 102°F. At the same time we are heating the digester, we’re actually cooling the engine.” Kluthe’s log books show that when the heat exchanger is taking heat off the engine for heating the digester it is actually keeping the engine cooler than when the engine is being cooled via the radiator. “In the corner is the GenTec – that’s the brains of the outfit,” says Kluthe, adding that an inline flow meter measures how many cubic feet of biogas is being produced. Primary and secondary filters deal with everything from heavy debris to moisture.
“Every operation has to have a name, so I named ours OLean Energy,” he adds. “Bacon Hill is the hog unit’s name – OLean Energy is the electrical generation unit.” The electricity produced is sold to NPPD under a “buy-all, sell-all” contract whereby the utility company continues to sell electricity to the farm for its power requirements and then buys all the generated output. “We get paid their ‘avoided cost,’ which isn’t much,” says Kluthe. He would like to be able to use his own energy and sell the surplus to the grid, and is working with the state legislators to make that possible.
Besides the revenue stream from electricity and minimizing odors, other benefits cited by the Kluthes include keeping methane out of the atmosphere and producing a nutrient-rich fertilizer. “Theoretically, the manure is in the digester for 21 days,” says Kluthe. “From there it goes down to a lagoon where it’s stored until it’s pumped out into the fields in liquid form.”
In the future, he predicts, there will not be a hog unit built or a dairy put in that doesn’t install a digester. “We’re on the forefront of something big. I think this is the future. Every day we feed the digester and the hogs replace that feedstock. It’s environmentally friendly, it takes care of the neighbors, and it produces energy – all of the aspects that you would want.”


Pagel’s Ponderosa is a 4,600-head dairy operation in Kewaunee, Wisconsin. The herd produces 120,000 gallons/day of manure, which is scrape collected from various barns and fed to a central location next to one of two GHD, Inc. digesters via a gravity flow system. From there the manure gets pumped into the digester.
The twin digesters have been operational since December 2008. “The main reasons we installed them were to have a constant source of bedding for our animals and for odor reduction,” says John Pagel. “I live on a farm where we have the digesters. Before, we had 1,500 cows and now we have 4,600. There’s a lot less odor now than there was then.”
According to a profile of Pagel’s Ponderosa Dairy in the Wisconsin Agricultural Casebook (available at, the solids content of the manure going into the digesters is about 7.5 percent. Biogas is treated with a condensate trap and chiller and run through a hydrogen sulfide reduction system. The scrubbed biogas powers an 800 kW Caterpillar engine generator set up to produce electricity and heat. Recovered engine heat is used to heat the digester and another building and will be used to heat a new facility and office space. A backup 4 mmBtu biogas boiler is also available for excess digester heat and will be attached to a radiant heating system beneath the floors of the new facility.
On-farm digesters are a good investment as long as producers receive a fair price for their power, says Pagel. “It’s great for neighborhood relations, but it still has to pay for itself.” Like hog farmer Danny Kluthe, Pagel is under a “buy-all, sell-all” contract with his local utility, but he counts himself fortunate that the company he deals with, Wisconsin Public Service, pays him a premium for the renewable energy produced. “I get a fraction more for the power I make than for what I use,” Pagel says. “We generate about 15 percent more power than we use in the summer and about 40 percent in the winter.”
Pagel’s Ponderosa produces about 56 tons/day of separated digested solids and sells about 27 tons a week to other farmers ($15 a ton FOB, $20 delivered). “We switched to bedding on digested solids for a year before we had a digester [at Pagel’s Ponderosa],” he adds. “We were buying it from other anaerobic digesters to try it out and see if we liked it as a bedding source.” The digested liquids are applied to the fields as a fertilizer source.
Pagel and a his partner Don Niles jointly operate another farm, Dairy Dreams, LLC in Lincoln, Wisconsin, where they recently installed a digester. Cows are still bedded on sand at Dairy Dreams, where the farm already had a lane separating sand, enabling it to be recycled and reused. “We wanted to see if this system would work with the digester,” he says. “If not, we can switch over to digested solids. We just started the digester two weeks ago.”

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