BioCycle March 2005, Vol. 46, No. 3, p. 53
Vermont Public Service Corporation works with a digester at Blue Spruce Farm to power its new green energy program.
Stephen Costello

Fifteen hundred dairy cattle of all ages – from heifers to mature milk cows – have become the newest energy generators in Vermont. Blue Spruce Farm in Bridport began producing electricity on January 13, 2005 as part of a renewable energy program with Central Vermont Public Service (CVPS). The farm is fueling an engine with biogas created by the anaerobic digestion of dairy waste for CVPS Cow Power programs directly linking Central Vermont customers with a farm owned generator. “This is one more way to diversify the farm, improve our bottom line, and manage our manure responsibly,” says Earl Audet, who owns the farm along with his brothers Ernest and Eugene and their families.
CVPS Cow Power, the state’s first voluntary renewable pricing program, has been awarded the Vermont Agency of Agriculture Commissioner’s Choice Seal of Quality. Customers can sign up to get all, half or a quarter of their energy through the program, which collects four cents per kilowatt-hour for the environmental benefit of the energy. That payment, along with 95 percent of the market price (Locational Marginal Price) for energy, goes to the farm generator. If not enough local farm generation is available to meet customer demand, the funds support other forms of renewable energy in the region, or the CVPS Renewable Development Fund, set up to provide incentives to Vermont farms to build methane generators.
“Our goal was to create a brand new market, allowing customers a renewable energy choice, and providing farmers with new income and manure management opportunities. We’re off to a good start,” notes Dave Dunn, CVPS program director. (His report, “Utility Turns Biomass Into Renewable Energy,” was published in September, 2004 BioCycle.)
The concept is relatively simple. Manure flows through a large sealed concrete tank, where it is heated with waste heat from the engine/generator. The gas is collected from the top to fuel the generator, and the manure by-product that is left after 21 days, has reduced odor, pathogens, and weed seeds. The liquid fraction will be spread on fields as fertilizer, and the dry solids can be used for animal bedding.
For Blue Spruce Farm, use of the by-product for bedding will save up to $60,000 annually. The farm received incentives from CVPS and state and federal grant programs to help get started. However, Blue Spruce has the largest share of the investment of its own funds in the project.
More than 1,100 CVPS customers have signed up for the Cow Power program since the Vermont Public Service Board approved the concept in August 2004, with dozens more enrolling each week. About half enrolled for 25 percent Cow Power, with the remainder evenly split between 50 percent and 100 percent. “Many of our customers want to vote for renewable energy with their wallets,” says a CVPS representative. “Support of farmers, the environment, and renewable energy are key factors. People seem to like that it’s local, it’s practical, and it’s benefiting dairy farm families who work the land and help keep Vermont looking like Vermont.”
Blue Spruce Farm is expected to produce about 1.7 million kWh of energy per year. Several other farms are considering the idea, some by combining their manure. Given current costs and expected revenues, it takes about 500 to 750 milking cows for the concept to be economically viable. The digester at Blue Spruce Farm was designed by Stephen Dvorak at GHD Inc, and the engine/generator was supplied by Marcus Martin at Martin Machinery.
Stephen Costello is with Central Vermont Public Service Corporation in Rutland, Vermont.