From the Fall 2008 issue of the Stewards of the Land newsletter

By Jon Halpin

As renewable energy sources go, the wind will blow and the sun will shine, but with even greater regularity cows will produce manure. A single dairy cow produces about a hundred pounds of manure a day— an abundant and renewable resource of riches that can power a farm, provide bedding for cows, fertilize fields, and create additional power that can be sold to utilities.

Several Vermont dairy farms have been at the forefront of using methane digesters to produce electricity. This technology extracts methane, the active ingredient in natural gas, from manure. The methane gas is then run through a generator, producing electricity.

Jon Ramsay, the Stewardship Agricultural Manager for the Vermont Land Trust, says more dairy farms are interested in digester technology. “Energy is a huge issue for dairy farms so everyone is looking for ways to reduce their energy costs and increase their profitability.”

David and Cathy Montagne run the Montagne Farm in St. Albans, where they milk 680 cows and produce over 15 million pounds of milk a year. In 2007, after several years of planning and preparation, they began using their methane digester to produce electricity. The Montagne Farm has averaged 5,000 kWh per day (the average home uses 650 kWh per month). That’s the product of 30,000 gallons of manure a day.

“The environmental part of what we’re doing means a lot to us, the bacteria, the odor, and the ozone,” says David. Methane is 20 times more effective at trapping heat in the atmosphere than carbon dioxide, the product of fossil fuel combustion. An open manure pit will release methane into the atmosphere. The digester eliminates that pollution, while also killing bacteria in the manure, reducing odor, and killing weed seeds.

The Montagnes’ methane digester was designed by GHD, Inc., a Wisconsin-based company. It is 74 feet by 120 feet and mostly below ground. Manure is collected from the barn and goes into an anaerobic digester, a below-ground, concrete structure. Within this oxygen-free space, bacteria breaks down the manure in about 21 days. Broken down, the manure emits biogas that is fed into a methane motor that turns a generator to produce electricity.

Electricity isn’t the only valuable product of the digester. A solids separator takes the remains and separates them into solid and liquid components. The liquid is a nutrient-rich fertilizer stripped of odor that can be stored in a lagoon and used on fields. The solid is a dry, odor-free substance that can be used as bedding for the cows or garden fertilizer. “We use it all,” says David. “We’re bedding the cows more than we used to, spreading liquid on the field more often now.”

The equipment that converts methane into electricity is expensive. A digester similar to the Montagnes’ generally starts at a quarter-million dollars. Add to that, a generator, a separator, and connection to the electricity grid and the investment can swell to between $1.5 and $2.5 million.

Central Vermont Power Services’ (CVPS) Cow Power program is at the forefront of supporting the generation of electricity at dairy farms. Customers who participate in the voluntary program choose to pay a premium of four cents for every kilowatt hour of electricity they use. That premium goes to the participating farms that sell their electricity to CVPS.

Preparing to install the digester and generate electricity was no small task. “We’re an established farm, we’ve undertaken large projects. And I wouldn’t have wanted to go into this blind and without a strong partner like my wife,” David says. David and Cathy have binders filled with the paperwork that came with the project. Contacting people, getting permits, and getting permission for the project took a year. After describing the ordeal, Cathy finishes with “And I would absolutely do it again.”

All told, including their own labor, the Montagnes estimate their expense at about $2 million, $800,000 of which was covered by grants from CVPS, the state, and the USDA. Factoring in the proceeds from the sale of electricity to CVPS, and the savings on bedding, David estimates a return of $300,000 a year on the system.

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Though producing energy is not considered an aspect of traditional farming, methane digesters that generate electricity generally do not come into conflict with VLT conservation easements. Jon Ramsay notes that four VLT-conserved farms have digesters that are or will be producing electricity. “We have no issues with sending power from methane out onto the grid.”

If a farmer is interested in constructing a digester, VLT staff first identifies the proposed inputs (the material going into the digester). If over 50 percent of the inputs—in this case, manure—are from the conserved farm then the methane digester is considered an agricultural structure and can be built within the farmstead area without approval, similar to other farm structures. The electricity generated from those digesters, whether used solely by the farm or sold on to a utility, is not a conservation issue. Some farmers have inquired if inputs from off the farm can be used as well. VLT can approve digesters with inputs of less than 50 percent from the farm, but written approval from VLT is needed prior to construction.

Energy-producing methane digesters have been mostly limited to larger scale farms. Cow Power’s participating farms range from the Montagnes’ 680 milking cows to Green Mountain Dairy’s 1,050. Farms on the smaller side of the scale, from 100 to 300 cows, face a range of hurdles, including a steep initial investment, working with developing technology, and adding upkeep to the list of daily chores.

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Two conserved farms in Charlotte have been grappling with these issues. The Nordic Farm, run by Clark Hinsdale, has had its digester running off and on for four years. Jonathan Foote, who manages the Foote Farm owned by Geneva Foote, is still waiting to start generating electricity three years into an experimental pilot program.

The Foote Farm has 160 milking cows and 90 young stock. “I got interested because electricity is expensive for me,” Jonathan says. “And, I’m especially interested in the bedding; sawdust has gotten pricey.”

Three years ago Jonathan was approached by Avatar, a company working to make modular digesters that would be suitable for farms with 100-1,200 head. Avatar agreed to finance and maintain the digester during the five-year pilot program. If Jonathan isn’t happy with the results at the end of the program, Avatar will remove the digester. “The technology is there, but it’s a matter of bringing the cost down for a 250-cow dairy to afford,” says Jonathan.

Unlike the Montagnes’ digester, Jonathan’s is all above ground, housed in a Quonset-hut-style building. The fiberglass holding tank is 80 feet long and eight feet high. The manure is pushed through the tank for 20 days, emerging into the separator at the end.
Three years into the experiment the results have been mixed. The digester is in place and running, producing gas, but as of yet no electricity has been produced. The separator, used to make bedding, was up and running for a time, but it broke and is waiting for repair. The growing pains of the project haven’t dampened Jonathan’s hope for the project’s success. “I didn’t think it would take so long, but it looks like we’ll have electricity here in a few weeks.”

His hope is that the digester will cover the farm’s electricity bills, around $1,200-$1,500 a month. It is also expected to produce about six yards of compost a day for bedding, and a thousand gallons of fertilizer a day. The digester is expected to come online very soon and Avatar is offering tours of the facility. “I think there’s a big interest,” Jonathan says. “I’m one of these experimental guys. If it doesn’t work, it doesn’t work. But this seems like the wave of the future.”

For Clark Hinsdale, on the Nordic Farm, the issue starts with what is to be done with the waste products of the farm. Making that waste useful is the goal; the digester is the means. “Dairy farms this size just create too much waste not to have a multifaceted way of dealing with it,” says Clark. The public will demand more from farmers as to how they deal with their manure.”

Nordic Farm is a 250-cow dairy. A farm the size of Nordic would usually expect a $2,000-3,000 a month electricity bill. Clark has a $4,000 a month bill, due to the robotic milking system and automated ventilation system. The methane digester, when working, was covering $3,000 of that amount, at times exceeding expectations. Clark says that “the record with the digester is spotty.” When it came online it produced electricity almost immediately. But in those four years he estimates that it has been producing energy only half the time. “In a good spell it would run weeks in a row, twenty-four/seven,” he says. “Then it would break down.”

Corrosion has been a major factor in the stoppages. “Manure is very corrosive,” says Clark. “Anything that wasn’t stainless steel—valves and gauges—failed from corrosion.” For all the troubles, Clark is optimistic: “I’m glad we did it. I would not yet call it a success, but I would not yet condemn it to failure.”

In talking about generating energy, Clark describes the methane digester less as an individual tool and more as a fulcrum in the farm’s daily operation. The creation of electricity is the end product, but the starting point is finding creative ways to handle the manure. “Putting electricity back into the grid may be an idiosyncratic way to manage manure, but the ability to grind, store, and move manure is a capacity dairy farms need anyway,” says Clark. “Long-term, it’s a facet of the environmental management of the farm.”

Funding Options for Farmers

USDA Renewable Energy and Energy Efficiency Program
This program provides grants and loan guarantees to farmers up to 25 percent of project costs, capped at $500,000. The next application deadline is June 18, 2009. Call (802) 828-6031.

Vermont Clean Energy Development Fund
This program supports the purchase and installation of methane digesters with low-interest (2%) loans and competitive grants. Call This e-mail address is being protected from spambots. You need JavaScript enabled to view it at (802) 828-4017.

VAAFM Renewable Energy for Agriculture Program
This grant program offers funding for planning, feasibility analysis, and business plan development. Most grants are for $10,000. Contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it at (802) 524-2216.

Green Mountain Power NEIL fund
Green Mountain Power makes grants available for renewable energy projects. Grant amounts are determined by the size and scope of the project. Funds can be used to offset the interconnection costs required to connect to the utility provider. Contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it at (802) 655-8531.

CVPS Renewable Development Fund
Interested farmers should contact Mike Raker, a consultant to the CVPS Renewable Development Fund, for a free anaerobic digester analysis, as well as help in selecting a digester vendor and negotiating the many grant processes. Mike can be reached at (802) 454-0123.