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.
“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
