Monday, May 5, 2008

Manure to Electricity

BRIDPORT, Vt. — Marie Audet's cows produce three things: milk, fertilizer and electricity.

They earn only about $13 per hundred pounds for the milk, a 25-year low, but 12 cents per kilowatt-hour for the electricity, a 4-cent premium over the market price.

That's why the Audet family and a growing number of other dairy farmers have decided there's money in manure. Power derived from manure is changing from an alternative-fuel experiment to a business, pushed by high oil costs, low milk prices and new laws restricting harmful gas emissions and requiring the use of renewable energy.

Two generators at the Audets' Blue Spruce Farm feed electricity to the local utility. They run on methane gas derived from cow manure. The farm is part of Cow Power, a program of the local electric company, Central Vermont Public Service. Cow Power gives customers the option to pay higher rates to subsidize farm-generated, poop-powered electricity. The 4-cent premium the farmers are paid helps cover the cost of installing an anaerobic digester that extracts methane from cowpies.

Now, after two years as Cow Power pioneers, the Audets are about to get company. Next month, Mark and Amanda St. Pierre, who run Pleasant Valley Farm a mile from the Canadian border, will become the second dairy farmers in Vermont to sell poop power. Four more Vermont farms are to go online in the next year. In California, six dairy farms have signed up to pump manure-derived methane into the pipelines of Pacific Gas and Electric.

Even proponents say methane digesters will never produce more than a tiny fraction of the energy consumed in the USA, even if all of the nation's 7,000 large dairy and hog farms installed them. But methane digesters can have a big effect on the economics of a dairy farm, the quality of life of its neighbors and on the pollutants a farm produces.

Unlimited quantities

As natural resources go, animal manure is abundant and endlessly renewable. Cow produces as much as 30 gallons a day, every day. "One thing for sure we can count on is a constant supply of it," Mark St. Pierre says.

Until now, the St. Pierres, like the Audets, stored manure in large open pits referred to as lagoons. Methane given off by the manure escaped into the air, contributing to the "greenhouse effect" blamed for global warming. The smell escaped, too, especially when manure was spread on fields as fertilizer.

Anaerobic digesters, also called methane digesters, solve both problems. Manure is swept from dairy barns by automated floor scrapers and goes down pipes into the digester, an insulated tank. The Vermont digesters are sunk most of the way into the ground.

The digester, which holds about three weeks' worth of manure, contains bacteria similar to those in a cow's stomach. The tank is heated and cooks the manure. The methane given off is piped away to fuel generators or flows directly to the utility's gas pipeline.

What remains is separated into liquid and a soft, odorless mulch like peat moss. The mulch is used as bedding for the cows instead of sawdust, saving the Audets, for example, $50,000 a year. The sawdust "was like gold," Audet says. With the "biosolids" from manure, she loves "having as much of that stuff as we want and making our cows comfortable." The Audets sell the extra as garden fertilizer.

The liquid is pumped into the old manure lagoons and then spread on fields as fertilizer, just as raw manure is on other farms. The thinner liquid soaks into the ground better than raw manure and minimizes runoff from fields into nearby Lake Champlain, Audet says. Perhaps the best part: It doesn't smell.

4 cents adds up

Farmers in the Cow Power program still pay for the electricity they use on the farm. But they produce more than they use, and they sell what they produce to the electric company for 95% of the wholesale price plus 4 cents per kilowatt-hour. The St. Pierres calculate that they'll gross $200,000 a year on the sales.

"Their 4 cents is what makes it go, on paper," Amanda St. Pierre says. The extra income is "definitely going to be a factor in our being here in the next 10 years."

Last month, grain giant Cargill agreed to go into business with Environmental Power, a New Hampshire company that installs methane digesters on farms, sells the gas to utilities and pays the farmers a percentage. Cargill will connect the company with the huge number of farms it does business with.

"We have folks out there running around" talking to farmers about installing methane digesters, says Albert Morales, executive vice president of Environmental Power. "But when you're a farmer and Cargill shows up and says, 'We think you should do this,' it carries more weight."

Already, Environmental Power has installed digesters at three farms in Wisconsin that sell electricity to their local utility and is building more at a feedlot in Texas that will sell methane.

Power of going 'green'

In California, Pacific Gas and Electric agreed last month to buy methane from six dairies where Environmental Power runs digesters. Pushing the utility is a new state law requiring power companies to buy 20% of their electricity from renewable sources by the year 2010. PG&E currently gets 12% of its energy from renewable sources, including wind, geothermal energy and animal waste, according to spokeswoman Darlene Chiu. California has also passed legislation requiring the reduction of greenhouse-gas emissions.

Central Vermont's Cow Power program is one of about 600 "green power" programs nationally, according to the U.S. Department of Energy, in which consumer agree to pay a premium on their electric bills, knowing that the extra money supports renewable-energy programs like wind or solar power. It's the only one that relies entirely on cow manure.

About 2.4% of the utility's customers have signed up, well above the 1.3% average participation in green-power programs.

Vermont's open farm fields and the impressive views — Audet's cows have a view of the Adirondack Mountains and St. Pierre's can see the Green Mountains — are what Cow Power buyers want to preserve. The rural landscape "is a non-renewable resource," Audet says. "That's why people want to pay the 4 cents."