“It was new for the guys at the dairy, and new for the cows, too.” – Doug Weaver, Digester Manager


By Brent Adams


For the past three years, Green Cow Power in Goshen, Indiana, has generated quite a buzz, and that’s not just because of the 3-plus megawatts of power it produces and puts back into its local electrical grid.

Through expansion and a significant investment in an innovative system that converts methane derived from manure and solid organic materials into energy, the third-generation dairy farming operation has created efficiencies that have led to better fertilizer for its 1,200 acres of crops, softer bedding for its cows, increased milk production and higher revenue.

At a time when trade tariffs and decreased demand have driven milk prices down and operational costs continue to rise, many longtime dairy-farming operations have been forced out of business. For example, in Wisconsin, which long has been billed “America’s Dairyland,” there were 8,372 licensed dairy producers at the beginning of September 2018, down 429 producers from the beginning of the year, according to Wisconsin Department of Agriculture, Trade and Consumer Protection data.

The transition to a power-producing dairy operation has helped Green Cow Power thrive in Indiana, where, as of July 2018, there were 986 dairy farms, according to the state Board of Animal Health’s Dairy Division. That is down nearly 60 farms from the start of 2018, said Doug Leman, executive director of Indiana Dairy Producers.

“Overall, I’d say adding a digester to our operation allows us to supplement and diversify our revenue outside of what you see in a traditional dairy farm operation, and that helps some with respect to being able to withstand the changes we’re seeing in the dairy industry,” said Green Cow Power’s digester manager, Doug Weaver.

“We’ve become a closed-loop operation,” Weaver added. “The manure from the dairy generates electricity that is sold to the utility as part of their renewables portfolio and the liquid and solid waste from the digesters serve as fertilizer for our crops and some of the neighboring fields, and also as bedding for our cows, respectively. We no longer have to buy sawdust for bedding. The bedding we use then re-enters the digester as a source of solid organic matter and the process starts all over again. Also, heat generated from the engines that power the generators provides hot water for the milk parlor floor heat and preheats our wash water. So, there’s a cost effectiveness benefit on several fronts.”

Leman said that at a time when existing farmers are struggling to sell enough milk to pay bills, it is imperative that dairy farmers follow Green Cow Power’s lead in thinking outside the box.

“Innovation is always important,” Leman said. “We need to be thinking about what new products we can make with milk, but we also need to be innovative in how we approach the business side of things. What we’re seeing right now is that some people are just trying to survive, while others are really optimistic about the future.”


Breaking down the process

Green Cow Power’s 1,700 cows produce about 50,000 gallons of manure daily. The farm had to increase its number of cows from about 750 to produce enough manure to supply its two, two-stage, mixed plug-flow anaerobic digesters, which have a total capacity of 5 million gallons. The digesters were made by Chilton, Wisconsin-based DVO Inc., which has been involved in biogas-to-electricity projects around the world.

In the digesters, the manure is combined daily with about 50,000 gallons of other organic waste, primarily from nearby food production facilities. Using this co-digestion method allows Green Cow Power to generate substantially more electricity than operators who run their digesters strictly off of manure, Parker said.

“To say that we can observe direct benefits on the farm from digesters while also diverting considerable waste from our landfills is pretty special,” he added.



At a temperature of about 101 degrees Fahrenheit, and with no oxygen present, bacteria break down the manure and other organic waste in a 30-day process that yields effluent waste, called digestate. Because methane is piped off during the process, digestate, a thin, black sludge, has all the nutrient benefits of the predigested manure, but without most of the odor. It is transferred to a 30 million-gallon lagoon on the Green Cow Power property. Annually, about 15 million gallons of the liquid, rich in potassium, nitrogen and phosphorous, is sold to farmers, who use it to fertilize their fields.

The methane is diverted to three generators, which produce energy that is transmitted to the Northern Indiana Public Services Co. substation in nearby Wakarusa, Indiana, Weaver said. It is estimated that the energy produced by Green Cow Power is enough to power about 1,900 homes for a year. That is a win for the utility company, which announced Sept. 19, that it plans to retire four of its five remaining coal-fired generation stations within five years, and retire the final one within a decade. That 1,800 megawatts of electricity production will be replaced with lower-cost renewable energy sources such as wind, solar, battery-storage technology and biogas.

When Green Cow Power’s digestion process is complete, solid post-digestion organic matter, now devoid of odor, is dried and trucked back to the dairy to be used as bedding. That has provided Green Cow Power’s dairy operation a weekly cost savings of more than $1,200. The solid material also is sold to local farmers as compost.


Do your research

Although making a significant investment to add digesters might not be feasible for some dairy farmers—the Green Cow Power project cost about $7 million to complete in 2015—Weaver said anyone in a financial position to do so should consider the benefits of turning manure into power.

“Research it. Figure out what all you need to make it run, both manure-wise and feedstock-wise,” Weaver said. “Make sure you have plenty of help and the right people involved at every stage in the process. Digesters don’t operate themselves. They need quite a bit of babysitting at different hours of the day and night.”

Weaver said Green Cow Power has two full-time employees who oversee the maintenance and operation of the digester and engines.

“We’ve found that the key to our success to have great employees,” Weaver said. “It takes more than a lot of money to keep these things running 24/7. We’re fortunate in that we have a great team of guys, some who work exclusively at the digester as well as a couple that are on the farm and lend a hand at the digester when necessary, who come together to ensure the operation runs well.”


Put the pieces in place

Weaver said a commitment from Green Cow Power’s local electric provider, NIPSCO, was a determining factor in convincing the farm’s owners to commit to the project.

“If your intent is to sell all, or part, of the electricity you produce, then securing a good contract with utility is key,” Weaver said. “If we wouldn’t have gotten a contract for the energy we generate, and at a favorable price point, it would have been useless to build this big.”

And in Weaver’s mind, bigger (when possible) is better.

“I’m a believer that it’s a lot easier to manage a larger digester than it is a smaller one,” Weaver said. “I think the big ones are just a better deal. They tend to be less finicky and some of the costs that you encounter in building are fixed costs that don’t change all too much if you go bigger.”

Weaver suggests putting in ample time talking to others who operate anaerobic digesters, to get an honest assessment of the risks and opportunities.

“We definitely tried to do our homework early on,” Weave recalled. “We spoke with quite a few digester owners beforehand, mostly out of Wisconsin, to observe their operations and to get some concept of the different models available. So, we got feedback from different folks who didn’t necessarily have a stake in the game in terms of our decision making.”


If you are interested in exploring the feasibility of adding an anaerobic digester to your dairy-farming operation, the U.S. Environmental Protection Agency, through its AgSTAR program, has online resources available to help farmers understand the preliminary planning and financing of such projects. The information can be found at www.epa.gov/agstar.

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