Methane generator taps the power of cows

WEYBRIDGE — Cow Power is coming to Monument Farms.
The methane digester program run by Central Vermont Public Service Corp. launched its Cow Power pilot program at Blue Spruce Farms in Bridport in 2005, and since then has added six more farms around the state. The digesters use cow manure to create electricity that CVPS buys from the farms and sells to environmentally conscious customers.
Monument Farms in Weybridge, as well as Dubois Farms in Addison, are part of a new wave of farms that will be producing electricity from manure. Construction of the digester at Monument’s Hagar Farm on Route 23 is under way, and Bob James, Monument Farms vice president of sales and marketing, said he expects the digester to go on line in the spring.
James said a methane digester is extremely costly — generally between $1.5 million and $2.5 million — and the high up-front cost can be prohibitive.
“The average farmer can’t just buy a digester,” James said.
But, he added, when the Rooney/James family that owns Monument Farms sat down to take a look at their options in 2008, a methane digester made sense for the ultimate savings it would yield. Early in 2009, when the farm received a $250,000 grant from the state’s Clean Energy Development Fund to support the project, the prospects looked even better.
The project hasn’t been without bumps. It received approval from the Public Service Board with a design by CH-Four Biogas Inc. of Ottawa, Ontario, but eventually it became clear that the round cement tank would sink into the ground over time unless it was supported by beams drilled all the way down to the bedrock — about 60 feet, estimated James.
So plans were drawn up for a new digester tank — one that is rectangular and will be more stable, according to James. It was designed by GHD, a Wisconsin company that has designed most of the digesters in the state. This digester was the smallest one GHD had ever created — the farm has just 500 cows, while many farms that pursue digesters have well over 1,000. While Monument Farms encompasses several other farms, James said that it would be inefficient to truck the manure in from other locations, and it made more sense to build a smaller digester.
The manure from the cows will go in one end of the digester and spend 28 days in the tank before it exits the other end. During that time, the methane gas will be extracted and pumped into a generator. The electricity from that gets routed into the power grid.
Meanwhile, the 28-day-old manure will get separated into liquid and solid matter. The liquid will go into the manure pond — James said it will be nearly odorless at this point — and the now sterile, solid matter will be used for animal bedding, instead of the sawdust that the company now imports from Canada.
James said that each truckload of sawdust costs about $2,400, and Monument Farms orders a truckload every few weeks.
While the digester tank is being built, Monument Farms must get Public Service Board approval for its revised plans before construction can begin on the building that will house the electric generator.
Once that gets powered up, though, James said the digester is expected to produce enough energy to sustain the business, and possibly more.
“We’re hoping there will be an excess,” he said.
CVPS is committed to pay a premium price for Cow Power electricity produced at new farms, which gives the Monument Farms project an additional payoff.
And James said the methane digester will be a good project to show to visitors and tour groups, of which the farm gets many.
“It’s a savings in electrical, and it’s a savings in the bedding it creates,” said James. “It will fit into our business nicely.”
Reporter Andrea Suozzo is at andreas@addisonindependent.com.

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