David Dunn is no stranger to poop jokes. In fact, for Dunn, as the manager of a program that converts cow manure into energy, they are an occupational hazard.

"One [person] likened my name, Dunn, to Cow Dung. Another called me the King of Crap, the Prince of Poo and the Sultan of Shit," he explained.

The name-calling may be in good fun, but Dunn's work is serious business. Currently, the Cow Power Program at Green Mountain Power in Rutland, Vt., which he leads, provides electricity for 2,500 customers from large quantities of anaerobically digested manure.

SPECIAL SERIES An occasional series showing how innovators are using garbage and farm wastes to generate clean energy. While the fuel may be free, the technology to make it a dependable source of energy and electricity is still a work in progress.

Proponents of anaerobic digestion, a process by which microbes in a hot, oxygenless environment break down manure and release methane, hope it gains broader traction nationally because of its environmental as well as potential economic benefits.


According to the Department of Agriculture, anaerobic digestion not only produces renewable energy from a waste stream, it also improves air quality, reduces odor and produces energy within a local community. And unlike other alternative sources of renewable energy, such as wind and solar power, electricity from cow poop can keep the lights on and air conditioning running 24 hours a day, seven days per week.

In an effort to promote the technology, the agency recently announced it would provide financial support for the construction of 500 anaerobic digesters over the course of the next decade. That would triple the number of digesters on livestock farms around the country, according to data from U.S. EPA's AgSTAR program. While those familiar with Cow Power say there are challenges to replicating it elsewhere, they point to it as an example of how the technology can be used successfully.

Using anaerobic digestion to locally generate electricity is not a new idea, but the way Green Mountain Power has adopted the technology is unlike most other places, according to Dunn.

He first proposed the idea for the program to then-Green Mountain Power CEO Bob Young in the early 2000s.

"His first response was, 'You're going to produce energy from cow manure? Holy shit!'" said Dunn. "He loved the idea, was a huge supporter of our efforts, and thought it would also have an impact on showing our shareholders what an innovative company we had."

Mooooving into development

Despite Young's approval, Dunn and his colleagues had to overcome big technological challenges to make the project work. First, the cement digesters that would be constructed on the dairy farms were much smaller than those that most utilities would prefer to work with. These digesters would be about the size of a cement swimming pool, large enough to handle about three weeks' worth of cow manure. The utility also had to figure out a way to incorporate the methane-gas-powered generators on the farms into the larger electrical grid.

David Dunn

Unlike typical electricity generation, which starts at a central point and is distributed outward along power lines, the farm-based generators reverse the flow of electrons from a remote location to populated areas. This can lead to voltage changes (and flickering lights) for customers. Adding the generators required major upgrades to an aging grid to better monitor power flow, according to Dunn.

"It took some convincing for our internal electrical engineers to really dive into this," he said.

Green Mountain Power also had to convince local farmers that those benefits would outweigh the approximately $1 million to $2.5 million price tag on setting up the technology. The utility forged its first partnership with the Blue Spruce Farm in Bridport, Vt., run by the Audet family. The farm's owners had already considered adding a digester on their farm for several years before Green Mountain Power approached them, according to Marie Audet.

"We were lucky to have this utility to get this project started. Instead of putting barriers in our way, they removed them," Audet said.

The farm began constructing its digester in the beginning of 2004, while Dunn and his colleagues were still seeking funding for the Cow Power Program. The utility was able to get financial support from Vermont's Department of Public Works and Agency of Agriculture. Former Sen. Jim Jeffords (I-Vt.), who died last year, had also helped to secure federal dollars from Congress. The utility used an insurance disbursement from the sale of its stake in the nuclear power plant, Vermont Yankee, to pay for a full-time project coordinator and grants for farmers.

Putting incentives to work

As Dunn and his colleagues were setting up Cow Power in the early 2000s, Massachusetts and Connecticut were beginning to set up a regional system for buying and selling renewable energy by trading renewable energy certificates (RECS). Since Vermont is part of the same regional electrical grid as the two states, the utility operators decided to create certificates for Cow Power at 4 cents per kilowatt-hour to trade on the regional market.

The utility also set up a 4-cent-per-kWh voluntary tariff on Cow Power. Customers who get all of their electricity from Cow Power pay about $20 extra per month, though many choose to get just a quarter of their electricity through the program. The farmers get a flat fixed rate for the energy they produce, plus the Cow Power premium, enabling them to earn around 18 to 20 cents per kilowatt-hour.

Green Mountain Power does not get any financial benefit from the additional cost it is charging customers. Instead, the funds go right back to supporting participating farmers, said Dunn.

"One reason is it's a good customer service opportunity, it also grows renewable energy in the state," he said.

By January 2005, Blue Spruce Farm's digester and generator were up and running, and the utility had recruited more than enough customers to the program. Over the past decade, the program has steadily grown to include 13 dairy farms in the state (17 projects in total).

Dylan Nelson, 23, is the newest and youngest farmer to join the program. He purchased the Nelson Boys Dairy LLC with his father, Chip Nelson, in 2013, and since the end of January, their farm has been producing between 175 to 200 kilowatts per hour in electricity for Cow Power customers.

"We are really excited to take this on, but we were a little skeptical at first," said Nelson. "There was a big fear that we would always be in there tinkering with [the digester]."

Financial cushion for the dairy business

The digester isn't quite at capacity yet, but once it is fully operational, they anticipate making between $20,000 to $30,000 in total revenue per month, which will offset their $7,000 to $10,000 monthly power bill. The extra income also provides a bit of a financial cushion for their business, especially since milk prices are half of what they were last year, according to Nelson.

Cows

Like other farmers in the program, the Nelsons also use the solid and liquid components of the digested manure to cut down on other farm costs. The liquid portion is an efficient fertilizer for the dairy's crops, and the solid portion is dried and used as bedding in place of sawdust for the cows.

To help keep the farmers' income from Cow Power consistent, Green Mountain Power also partners with about a dozen Vermont businesses. One of those partners is Killington Mountain Resort & Ski Area in Killington, Vt., which has purchased Cow Power for the past 3½ years.

"It kind of fell into our laps. We thought the value was intrinsic and not a dollars and cents issue," said Killington's communications and public relations manager, Michael Joseph.

In its first year, the resort purchased 300,000 kWh of electricity to power its K-1 Express Gondola -- visitors can recognize it from its cow-print design. Now Killington is purchasing over 1 million kWh annually and is using Cow Power year-round. In addition to the gondola, the electricity from Killington's Peak Lodge is also offset with Cow Power. Although the resort pays a $4,000 premium for 100,000 kWh of electricity per month, Killington uses its adoption of the local renewable energy to boost its public profile, according to Joseph.

Vermont Hard Cider Co., maker of Woodchuck Hard Cider, has also partnered with Cow Power for the past five years. The cidery gets a quarter of its electricity from Cow Power and sends its organic waste back to a digester at Monument Farms, a nearby dairy that participates in the program, according to Cheray MacFarland, the company's marketing operations manager.

While Cow Power has proved to be successful in Vermont, the program may be difficult to replicate elsewhere in the country, according to a USDA representative. Farms in Vermont may be separated by just 5 to 10 miles, whereas farms in Montana could be 100 miles apart. Green Mountain Power also has the advantage of having a few thousand customers willing to pay for green energy, while in other states, perhaps only a few hundred might be interested, he said.

Competing with rooftop solar

A report released by the Innovation Center for U.S. Dairy in 2013 also found that selling electricity production alone from anaerobic digestion did not provide enough of an economic return for large dairies of 500 or more cows. However, farms that monetized captured nutrients like nitrogen and phosphorus and traded them on a carbon market would be able to make the technology financially worthwhile.

As Cow Power moves forward, Dunn is working on evolving the program's model to make it feasible to more farmers. He also says he wishes it had more customers.

"At present, the biggest competition is customers building solar panels on their homes. We've lost customers to the solar industry, but that's where we use the regional market," he said.

Despite the competition, the program is working to expand to include smaller dairies, but with the utility owning and operating the digesters instead of the farmers.

For dairy farmers like the Audets and the Nelsons, being a part of Cow Power has helped to close the resource loop on their farms, turning waste into useful product.

"When we started this, we had no idea that the country and people would have been so interested in it," said Audet.

Since beginning the project, the Audets have expanded their involvement in the program by building a second digester. The Nelsons are experimenting with ways to use heat generated by the machinery within their dairy to make their operations even more efficient.

"We're pretty proud of what we've done," said Nelson.