October 19, 2011 | General

Vermont Builds Anaerobic Digestion Capacity

BioCycle October 2011, Vol. 52, No. 10, p. 38
State, federal and public utility grants, combined with favorable feed-in tariffs, have led to investment in AD systems and biogas utilization.
Diane Greer

MUCH activity related to anaerobic digestion has been happening in the State of Vermont. New projects have been started in the agricultural, municipal and industrial sectors.
State, federal and utility incentives have helped to spur digester development in Vermont. For example, a feed-in tariff program called Vermont SPEED (Sustainably Priced Energy Enterprise Development) pays a premium over regional wholesale electricity prices. An electricity production incentive worth 4 cent/kWh paid over five years is provided by the Central Vermont Public Service (CVPS) Cow Power program. “It has been multifaceted,” said David Dunn, Cow Power project coordinator. “We are all pulling in the same direction to really help these projects move forward.”
At the Monument Farms Dairy in Weybridge, a $1.9-million anaerobic digestion system processing manure from 500 milking cows started producing biogas in June. The biogas fuels a 155-kWh engine generating electricity. The actual interconnection to the grid became live in mid-September. “We’re running 80 to 105 kWh, 24 hours a day,” says Cliff Carpenter of Monument Farms. “As of noon today [9/29/11], we had generated 27,524 kW.”
Monument Farms Dairy processes, bottles and distributes 34,000-pounds of milk daily. About three years ago, the dairy decided to install an anaerobic digester to produce a less expensive source of cow bedding. “We bed with sawdust,” explains Peter James, one of Monument’s owners. “Sawdust was becoming harder to come by and very expensive.” Carpenter adds that the dairy has been producing its own bedding for about a month. “We’ve eliminated purchasing sawdust from Canada for this period,” he notes. “We will still need a small amount in the future, but we’ve cut the cost of $3,000/month out, as well as the tractor trailer delivery from Quebec to Weybridge every two weeks.”
High electricity prices and a desire to improve the farm’s sustainability and viability for future generations also drove the decision to install the digester. After a false start to build a digester with a Canadian company, the farm opted for a 400,000-gallon GHD modified plug-flow digester. Initially the digester will process cow manure. James is looking at adding wastewater from the bottling operation and may codigest off-farm waste in the future.
Heat from the engine producing electricity warms the digester and supplies a radiant heating system in the floors of the bedding storage area. Effluent is dewatered, with the liquids returned to the manure pit for later land application and the solids dried for bedding.
The dairy is receiving 14 cents/kWh for electricity sold to CVPS under SPEED. Authorized under a 2005 Vermont law, SPEED was amended in 2009 to create standard offer contracts, a type of feed-in tariff for renewable energy projects producing under 2.2-MW of power. “The feed-in tariff really accelerated the pace of digester development,” Dunn says. CVPS Cow Power provides an additional 4 cents/kWh. Cow Power is a voluntary program where CVPS customers elect to pay a premium of 4 cents/kWh over standard electricity rates.
The Cow Power Renewable Development Fund awarded a $125,000 grant to the Monument Farms project. The fund is primarily supported by a benefit from an insurance policy that CVPS held as a former owner of the Vermont Yankee nuclear power plant and excess money collected at the beginning of the cow power program when voluntary demand outstripped the supply of renewable farm power.
The project also received a $250,000 grant from the Vermont Clean Energy Development Fund (CEDF) and a $50,000 grant from the Vermont Department of Agriculture for Best Management Practices. The USDA Rural Energy for America Program (REAP) program chipped in a $290,520 grant and $500,000 loan guarantee. “Every single program that we have received a grant from has been critical to the project,” James says. The CEDF was created by the Vermont Legislature in 2005 to increase the development of renewable energy and combined heat and power technologies. Its funding was derived both from agreements with Vermont Yankee and monies from the 2009 American Recovery and Reinvestment Act.
The Monument Farms project also expects a Section 1603 U.S. Treasury grant for 30 percent of eligible project investments. The grants, which were part of the 2009 stimulus legislation, are applied for and awarded after the project is completed. The grant program is set to expire at the end of 2011, although the American Biogas Council and others are encouraging Congress to pass an extension (see Anaerobic Digest in this issue for details).

The Chaput Family Farm in North Troy completed a $1.8 million digester project in summer 2010. The 1,800-acre farm milks 830 cows and produces 62,000 pounds of milk daily. RCM International designed the 906,000-gallon complete mix system to treat manure and wash water from 1,000 milk cows and 600 replacement stock. The farm also codigests a few truckloads of fish processing waste weekly. Biogas produced by the system fuels a 300-kW genset supplied by Martin Machinery sized to produce 1.6 million kWh of electricity annually.
Chaput, the first dairy in the SPEED program, receives 16 cents/kWh for its power and an additional 4 cents/kWh through Cow Power. (SPEED has since adjusted the tariff paid to farm methane projects to 14 cent/kWh.) The project received a $100,000 Cow Power grant and a grant and loan through USDA REAP.
The Dubois Farm in Vergennes completed installation of a $2.6 million GHD digester in November 2010. The digester processes manure from the farm’s herd of 1,200 cows that produce over 30 million pounds of milk annually. The digester is sized to handle manure from 1,800 cows. A biogas-driven 450-kW engine is expected to generate 2.7-million kWh of electricity annually. Cow Power awarded the project a $175,000 grant, USDA REAP provided a $500,000 grant and $500,000 loan guarantee. The project sells electricity under SPEED and receives a 4 cent/ kWh premium from Cow Power.
In April, Avatar Systems installed an anaerobic digester system at the 170-cow Keewaydin Dairy Farm in Stowe. Avatar’s mixed-plug flow system is composed of horizontal fiberglass hulls, 20- and 40-ft. long. Hulls are linked to accommodate the range of manure volumes found on small to mid-sized farms. The 22,472-gallon digester processes manure from 75 milking cows and is expected to produce about 5,000-cubic feet of biogas daily. Biogas will fuel an I Power 20 kW generator. CEDF provided a $250,000 grant to fund the project.
Other dairy digester projects currently under development in Vermont include:
• Kane Cow Power, LLC recently completed construction of a GHD digester system on the Kane Scenic River Farm in Enosburg Falls, sized to process manure from 850 cows. The digester is filled and biogas is being flared until the connection with the utility is finished (expected by the end of the month). A 225 kW engine is installed. Digestate will be used as fertilizer and cow bedding.
• Four Hills Farm in Bristol just began construction of a GHD digester capable of generating 450 kW. Dewatered solids will be used for bedding and sold to nearby farms and nurseries. Heat from the generators will produce hot water for the farm.
• Blue Spruce Farm in Bridport, the first dairy joining the Cow Power Program in 2005, is adding a second GHD digester that will accommodate herd expansion and relieve capacity issues with the first system. The biogas will fuel a new 600-kWh Guascor genset. Heat from the engines will produce hot water for cleaning milking equipment and for radiant floor heating in the winter. The digesters will produce more bedding then required by the farm; the excess will be sold to other farmers.

In April 2011, the town of Brattleboro began a $32.8 million project to upgrade the Brattleboro Wastewater Treatment Facility. Much of the equipment and infrastructure at the 43-year old plant had reached the end of its useful life, explains Gene Forbes, senior vice president of Hoyle, Tanner & Associates, the project’s designer.
To meet the town’s sustainability commitments, the project is designed to reuse existing facilities and structures to the extent possible and upgrade the biosolids treatment operation to produce Class A biosolids that can be land applied. The three existing digesters will be converted into a two-phase anaerobic process. Two of the digesters will be renovated for reuse as mesophilic digesters. The third will be operated as a sludge storage and equalization tank. A new thermophilic digester will be built. Construction includes three new feed sequencing tanks for flow equalization, heating and homogenization.
Biogas from the upgraded digester plant will fuel a 65-kW Capstone microturbine producing heat and electricity for the WWTP. Currently the digester biogas is flared. All sludge pumps, piping, gas compressors, heat exchangers and boilers will be replaced. Two exhaust heat recovery units will capture waste heat from the microturbine. The design includes a new facility for receiving and storing up to 10,000-gallons of hauled wastes daily including septage, fats, oils and grease (FOG), and other high strength wastes. Hauled wastes will primarily be treated by the digesters, which have been sized to handle the additional volume.
The project received a $50,000 design/study grant and a $250,000 construction grant from CEDF for digester optimization and the cogeneration systems. Construction is on a two-year schedule, but Forbes believes the contractor will finish ahead of schedule.
Hoyle, Tanner will complete work later this year on upgrades and the expansion of the Airport Parkway Wastewater Treatment Facility in South Burlington. The design increases plant capacity from 2.3-million gallons per day (MGD) to 3.3 MGD. The digester system will be converted to a two-phase process by retrofitting the three existing mesophilic digesters and adding a fourth thermophilic digester. A waste activated sludge (WAS) tank and thickening equipment are being installed prior to digestion. The thickened WAS will be pumped to a digester feed sequencing tank where it will be blended with primary sludge and septage prior to digestion. The project received a $250,000 CEDF project assistance award for the installation of the biogas-fueled cogeneration plant that will produce heat and power for the facility.
Utilization of microturbines at WWTPs in Vermont is not new. The Essex Junction Wastewater Treatment Facility processes 1.9 MGD of wastewater. Prior to 2003, the plant flared 45 percent of its digester methane and burned the rest to provide heat for the digestion process. In 2003, Essex Junction installed two 30 kW Capstone microturbines to use 100 percent of the biogas to generate electricity that is used onsite to power pumps and other water treatment equipment.

The Magic Hat Brewery in South Burlington became home to a high solids digester in mid 2010. It was built and is owned and operated by Purpose Energy based in Waltham, Massachusetts. On average the brewery, which runs three shifts, five days a week, produces 30,000 gallons of wastewater, 10,000 gallons of spent yeast and 20 tons of spent grain a day. Wastes are mixed in an equalization tank and fed to the high solids digester. Three reactors process the waste in series.
Biogas is first used to replace natural gas in the brewery’s boiler. Eric Fitch, Purpose Energy’s founder, says the digester almost eliminates the brewery’s use of natural gas. When the brewery is not operating, biogas is fed to a dual-fuel 330-kW genset; electricity is sold to Green Mountain Power under a power purchase agreement. Purpose Energy earns revenues from tipping fees and energy sold to the brewery.
The brewery is also up against its ceiling for BOD discharge at the WWTP, Fitch says. Pretreating the wastewater in the digester lessens the demands on the municipal treatment plant and gives the brewery the ability to grow. “That is a big upside for them,” Fitch says.
The digester operated for 6 months then was taken offline in December 2010 to make platform improvements. Modifications included addition of condensation equipment to remove particulates and moisture from the biogas. The digester was brought back online in June 2011. Purpose Energy, which is primarily funded by private equity investors, received an $850,000 CEDF loan to help finance the project. A U.S. Treasury 1603 grant helped pay for upgrades to the gas handling system.

While a lot of digester work is underway in Vermont, the outlook for continued development is not bright. State funding sources for digester projects are drying up. CEDF funds have largely been depleted and there is uncertainty how Vermont Yankee may support the fund after its current operating license expires in March 2012.
The Cow Power renewable development fund is also running short of funds. When the ninth Cow Power farm came online this summer the demand from Vermonters willing to pay a premium for energy just about matched the supply of energy provided by farmers in the program, Dunn explains. To attract more customers, Cow Power is focusing some of its funding on marketing the program. “We can’t pay the 4 cent production incentive if we do not have the customers,” he says.
The Cow Power grant program will receive one more insurance installment in 2012. “Beyond that it is uncertain,” Dunn says. If marketing Cow Power succeeds at collecting more money than required to pay the 4-cent premium, the excess money can be rolled into the grant program.
Michael Raker of Agricultural Energy Consultants, LLC in Plainfield, Vermont, who has worked with farm digester projects, has been told not to depend on funds from the State’s Agricultural agency. “Our state is struggling like other states so we really are in a bit of a fix,” he says. Meanwhile budget cutting in Washington threatens key programs, including REAP. “REAP has been a huge factor in getting projects done in Vermont,” Raker adds. “That will be a difficult hurdle to overcome if that program is cut.”
Funding from USDA EQIP (Environmental Quality Incentives Program) and REAP are necessary because Vermont dairy farms are smaller than farms in the rest of the country, Dunn says. “Based on the scale of our farms we need as much incentive funding as we can get to offset some of the costs.” Dunn believes funding these projects is a good investment for taxpayers since they provide great societal fringe benefits as well, such as reducing methane emissions and lessening odors from manure.

Diane Greer is a Contributing Editor to BioCycle.

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