How do you turn a reserved, soft-spoken New England dairy farmer into a media celebrity? Help her to buy and install a profitable anaerobic digester. Marie Audet, owner of Blue Spruce Farm, a modest-sized 1,000 cow dairy, has become the unofficial spokeswoman for Cow Power, Vermont's most innovative energy program. By processing 30,000 gallons of manure a day, her dairy's digester sends profitable electricity to the state grid, while eliminating a problem that had always bothered her – the strong, annoying odor of decomposing manure coming from lagoons right behind her family's milk barn.
And if you build it they will come, wether you expected them or not: Marie has already shown the farm to over ten thousand people, including Chinese teenagers, Hawaiian tourists, and environmental journalists; her farm has also been covered on CBS Evening News, German and U.S. public radio, and on Planet Green TV:
Hatching a plan to save Vermont's cow-centric lifestyle
Few states have the pastoral quality of Vermont, and, for many residents, it's the rolling hills, grazing cows, and colorful barns that maintain that iconic beauty. But about ten years ago, as low milk prices kept eating away at Marie Audet's razor-thin profit margins, and as other dairies shut down across the state, she realized that her dairy would have to innovate just to survive. Meanwhile, her small local utility, Central
Vermont Public Service (CVPS), which relies primarily on nuclear and hydro for power, was developing a new business model to save the dairies and the state's quaint, picture postcard lifestyle – because with a population ratio of 600,000 people to 300,000 cows, their fates were completely entwined.
Looking for a source of reliable distributed energy, CVPS's Cow Power project leader, David Dunn, decided anaerobic digesters were the way to go. But there was a huge hurdle: they were too expensive, costing more than the wholesale electricity prices charged to support them.“Even though the technology had existed for years, it hadn't gained acceptance,” Dunn said
, adding, "they were too expensive to build, operate and maintain." But he found a way around that.
After the Vermont state Legislature passed a bill in 2000 allowing utilities to create a voluntary option to support renewable energy, Dunn pushed CSVP to start a program where customers could pay an extra 4 cents per kilowatt hour for cow-powered electricity knowing it would benefit farmers and support renewable energy. “People laughed at the notion of asking customers to pay a little extra for something they believe in,” said Dunn
, but the voluntary tariff became available in 2004.
Marie Audet buys her first digester
Dave Dunn approached Marie Audet, her husband and brothers, about installing Cow Power's first digester at their dairy. The new revenue he promised by selling power to the grid was appealing, but the deal was sealed after he demonstrated that they could save $2,000 a week by replacing expensive sawdust bedding with solids from the digester. Their new $1.3 million digester began operation in 2005.
The whole process begins with the Audet's 1000 milk cows, each capable of producing
30 gallons of manure a day. A scraper that looks like squeegee on wheels moves slowly and constantly as it collects 30,000 gallons of manure falling on the rubber-coated barn floor every day; the manure is then pumped into the huge 600,000 gallon digester, which is like a concrete in-ground swimming pool with a cover; methanogenic bacteria digest the manure for 21 days at a constant temperature of 101 degrees; finally methane gases collect at the top of the digester, where power generators send electricity to the grid, powering about 250 homes or businesses paying the dairy $250,000 a year.
The watery waste that flows out of the digester is pumped to an auger-style compressor that separates the liquid from the solids, the undigested plant fibers. Earthy-smelling, soft to the touch and resembling peat moss, the solids are used as bedding for the cows instead of expensive sawdust, and saves the dairy $100,000 a year.
Microbes in the digester have converted most of the volatile fatty acids into odorless methane, and so the liquid byproduct is far less potent. Nearly odorless, it is pumped to the holding pond and spread on the fields as fertilizer.
Cow Power's satisfied customers
One of Cow Power's first large customers was Green Mountain College, which committed to purchase 50% of its main campus’s electricity from Cow Power. “This is a
great step for us toward a sustainably powered campus,” said the college's provost. “We are very happy to be supporting the regional economy and the family farms that are so important to the Vermont way of life.”
Today, Cow Power has about 3,500 customers. The ten dairies in the program have produced almost 53 million kilowatt hours of renewable energy. Customers have paid more than $3 million in 4-cent premiums, Dunn said.
Vermont's open farm fields and the impressive views – Audet's cows have a view of the Adirondack Mountains – are what Cow Power buyers pay to preserve. The rural landscape "is a non-renewable resource," Audet says. "That's why people want to pay the 4 cents."