Plying Poop Power in Portsmouth

Hogs and dairy cows in the United States produce nearly 3 billion pounds of manure a day, according to the U.S. Department of Agriculture. That’s over 1 trillion pounds per year—an unimaginable, truly Augean heap of waste. Unfortunately, farmers can’t simply divert a few rivers, as Hercules did, to wash it all away. But technology is creating some promising alternatives, and a Portsmouth, NH, company called Environmental Power is exploring one of them. It’s building North America’s largest facility for producing pipeline-quality natural gas from cow manure.

Call it re-moo-able energy. Outside Stephenville, TX, about 60 miles southwest of Fort Worth, an Environmental Power subsidiary called Microgy is constructing eight above-ground anaerobic digester tanks, each holding 916,000 gallons of manure. When high-carbohydrate materials such as restaurant grease-trap waste are added to the manure and the mixture is heated to about 130 degrees Fahrenheit, the bacteria naturally present in the manure will really start to party, breaking down the waste and releasing an expected 1 billion cubic feet of methane per year.

The captured biogas will be purified, compressed, and pumped directly into a nearby natural gas pipeline. The Stephenville plant is the kind of place that’s sure to turn up sooner or later on an episode of the Discovery Channel’s cult hit “Dirty Jobs with Mike Rowe.” And it’s one of the world’s first industrial-scale implementations of a technology that’s already widely used for small-scale electrical cogeneration on farms in Europe and has the potential to convert a decent fraction of U.S. agricultural waste into usable energy.

Environmental Power’s Huckabay Ridge Plant“We are energy guys, and we’re really focused on trying to identify ways to maximize the production of useful energy,” says Mark Hall, a senior vice president in Environmental Power’s Chicago office. “So we were looking for a [variant] of anaerobic digestion that we could deploy for larger operations to maximize gas production. This technology works really well for that.”

Environmental Power was founded in 1982, and over the years it has developed, operated, and sold a dozen clean-energy projects, including seven hydroelectric plants, two facilities that burned municipal waste, and three waste-coal-powered generating plants. In 2002 the company acquired Golden, CO-based Microgy, which had obtained the North American license for an anaerobic digestion technology developed by Danish firm Xergi. “This thermophilic co-digestion technology—where you use a little higher temperature and a mix of materials in above-ground digesters—has been used pretty extensively in Europe, including over 2,500 installations in Germany” says Hall. “It’s on the high end, from a capital-expense standpoint, but it really produces a lot of energy. And we are honestly pushing the boundaries and trying to achieve large-scale, pipeline-quality gas production.”

Selling the methane alone would produce respectable revenues for the company. But the waste-digestion business has a few built-in incentives that make it even more attractive—from a financial standpoint, if not an olfactory one. One is that the basic material is free. Farmers are usually glad to have someone take manure away, according to Hall. (In fact, in some cases the company can collect “tipping fees” for getting the manure off of a farmer’s property.)

Another is that clean-energy projects like anaerobic digestion plants allow their owners to participate in the magical pseudo-economy of renewable energy certificates and carbon credits. An REC, also called a renewable energy credit or a “green tag,” is a tradeable commodity certifying that one megawatt-hour of electricity was generated using a renewable energy source. If a utility generates one megawatt-hour of electricity using natural gas that it bought from Environmental Power, it is then entitled to sell one REC.

Since natural gas from a renewable source generates this extra value, Environmental Power is able to charge the utility a premium for it. But get this: Because methane is a potent greenhouse gas—trapping heat in the atmosphere even more effectively than carbon dioxide—Environmental Power is also entitled to a separate carbon credit or “certified emission reduction” by virtue of the fact that it captured the methane in its digesters, rather than allowing it to dissipate into the atmosphere as it would have if the manure had gone into one of the lagoons found on most dairy farms. The company can sell that credit directly to anyone looking to buy “carbon offsets”—pledges that one person or organization has reduced its greenhouse-gas emissions by a certain amount in order to counterbalance someone else’s emissions.

Opening Day at Environmental Power’s Stephenville Plant“It’s a triple whammy,” says Hall. “We sell the gas, we get the added value for the REC, and we sell the carbon credit.”

It’s really a quadruple whammy, since, as noted above, the raw material is free. But it doesn’t stop there. Believe it or not, the liquid waste left over from Environmental Power’s process can be sold back to farmers as nitrogen-rich fertilizer, and the solid material—mostly undigested grass—can be dried and re-used as animal bedding. “It’s light and fluffy and the cows are pretty comfortable in it,” says Hall.

Prospects are so bright that Environmental Power is designing and breaking ground on several new facilities in Nebraska, California, and Texas even before the Stephenville plant has been completed. Of course, there are plenty of complications that could reduce or delay the profitability of Environmental Power’s project. For one thing, high-temperature digestion is an unstable process that’s tricky to manage correctly, especially in tanks holding almost a million gallons of manure, Hall says.

And the company can’t build its facilities just anywhere: they have to be adjacent to a large manure source (i.e. a large dairy or cattle herd or hog farm), close to a gas pipeline, and not too far from a metropolitan area with lots of grease-rich restaurants. The lack of large herds in New England means Environmental Power won’t be building any facilities near its Portsmouth headquarters, but Hall says upstate New York could become home to anaerobic digestion facilities, as could Virgina, the Carolinas, and other Southeastern hog havens.

Just how big is Environmental Power’s potential market? “It’s hard to quantify,” says Hall. “It’s like a map with many layers—you have to overlay where the farms are, and where the pipelines are, and the relative value of energy commodities in different areas of the country. But 3 billion pounds every day—that’s a lot of manure. We think the market is very significant.”

Wade Roush is the producer and host of the podcast Soonish and a contributing editor at Xconomy. Follow @soonishpodcast

Trending on Xconomy

By posting a comment, you agree to our terms and conditions.

4 responses to “Plying Poop Power in Portsmouth”

  1. Carl Hansen says:

    Intrepid Technology of Idaho Falls, Idaho is already producing pipe-line quality gas from manure at their facility near Rupert, Idaho. The facility is on a 6000 cow dairy North of Rupert (see

  2. Great idea. I have been told that cows are serious producers of methane in the UK at least and a potential threat to the environment.
    best of luck with your project.