ADDISON — The Dubois Farm in Addison this week flipped a switch and brought its methane digester on line.
The $2.6 million digester is expected to generate enough power to run 400 homes, and it will take its place as the 10th working digester in Vermont — including the one at Foster Brothers Farm in Middlebury, which has been in operation since the 1980s.
Dubois is the first of three Addison County projects that will be joining Central Vermont Public Service’s Cow Power program in the year ahead — Monument Farms Dairy in Weybridge and Four Hills Farm in Bristol will be coming on line during the spring and summer of 2011.
Cow Power projects capture methane from manure and turn it into electricity.
Bernard Dubois, who owns the third-generation dairy farm with his two brothers, said the farm will likely save a couple hundred thousand dollars each year with the power produced by the digester, but that it is difficult to say exactly how long it will take to pay off the price of the equipment. Although USDA and state grants funded about a third of the digester’s cost, the expense is still substantial.
But if the potential payoffs hadn’t been clear, Dubois said he would never have taken on the project.
“I did not originally think that we would have one of these,” he said. “I looked at the Audets’ (digester) when they first started, and I wasn’t sold on it.”
But as time went on and the technologies advanced, he said it was an easier project to justify.
The digester process yields benefits even beyond the methane gas harvested to run a generator. Manure from the farm’s 1,200 cows will flow into the 16-foot-deep, sealed tank, the methane gas is filtered out and, after three to four weeks, the nearly odorless mixture that remains will flow out the other end.
The solids and liquids are separated, and the liquid goes into the manure pond, then onto the fields as fertilizer — which, said Bubois, could turn out to be a more effective form of fertilizer than the unprocessed manure.
The solids, now just organic matter, are dried and used as bedding for cows — which, while it will not completely eliminate the farm’s need to bring in truckloads of sawdust each week, will help offset sawdust use and costs. Dubois said that the farm spent $176,000 last year on sawdust.
Dave Dunn, manager of renewables at CVPS, explained that the price of sawdust has jumped in recent years due to a rise in demand. Farmers are paying a premium for the product because many companies are making sawdust into pellets to power a growing number of wood stoves in homes.
In what Dubois hopes will be another significant savings, the hot water that circulates through the engine will be piped across the yard to the milk tanks, where it will be used to help heat the milk.
Dunne said that the digester’s additional uses and its steady operation — the generator never stops creating electricity, except when it is down for maintenance — help to make it a unique alternative power source.
“Wind and solar don’t have side benefits,” he said.
A FULL SYSTEM
Dunn said that the methane gas creates electricity and carbon dioxide once it is filtered through the brightly-colored tubes in a new building off to the side. While carbon dioxide is a greenhouse gas, like methane, Dunn said it has 1/20th the impact of methane gas.
This reduction in greenhouse gases is one of the things that draws the 3,500 participants in the voluntary Cow Power program to pay a premium price for their electricity — $0.04 per kilowatt-hour (kwh) over the standard price.
When the program started, CVPS paid the farmers the going rate for electricity, which hovered around $0.11 per kwh. After that, the additional $0.04 premium from Cow Power subscribers went directly to the farmers.
“It was not a huge revenue stream,” said Dunn.
Since 2009, when the Vermont Legislature established the feed-in tariff in an attempt to stimulate the growth of renewable energy, farmers have been guaranteed a kwh price of $0.14 for their power, along with the additional premium from the consumers. A small group of farms — including Dubois Farms — were locked in at $0.16.
Other farms already enrolled in the Cow Power program, while not guaranteed a higher price in the original wording of the legislation, petitioned for a change in the law’s language and are now receiving a price of $0.14 per kwh, which is the current standard rate for Cow Power farms.
Dunn said the provisions of the feed-in tariff won’t last forever — each type of renewable is capped at a certain percentage of the state’s total energy production, and projects begun after that cap has been reached do not receive the same premium. The feed-in tariff price was locked in at a high $0.30 per kwh for solar electricity projects, and the cap has already been reached.
On the statewide scale, said Dunn, Cow Power will never amount to a large source of power in the state — most of the larger farms in the state are already operating digesters, and new digesters are being installed on smaller farms, meaning less power generation per unit.
With the new farms coming online, it is nearing a 1 percent share in the state’s electricity needs, while the Vermont Yankee nuclear plant produces between a third and a half of Vermont’ power needs. But Dunn said that as the state moves toward phasing out Vermont Yankee, Cow Power will continue to be an asset.
“It won’t replace Vermont Yankee, but it’s a nice piece,” said Dunn.
Reporter Andrea Suozzo is at [email protected].