Cow Manure, Other Homegrown Energy Powering U.S. Farms

From wind to sun to cow pies, rural regions are full of natural resources that can be used to make renewable energy (above, cattle rest under windmills at a Canadian wind farm). Across the United States, many farmers turning this homegrown electricity into a new crop.Photograph by Steve Winter/NGS Maggie Koerth-Baker National Geographic News

From wind to sun to cow pies, farm-based natural resources are supplying an increasing number of U.S. farmers with homegrown sources of renewable energy.

Farm-based energy can save money and even become a new source of income by powering nearby homes, for instance.

Traditional energy sources are expensive: In 2008 fuel and fertilizers—which are largely made from natural gas—accounted for 12.5 percent of all farm expenses. (Learn more about sustainable agriculture.)

Homegrown energy may also lessen the impact on the environment by avoiding fossil fuels.

Food production—not counting factors such as processing and shipping—accounts for one to 3 percent of U.S. energy consumption and about 7 percent of its direct greenhouse gas emissions, according to the U.S. Department of Agriculture (USDA) and the nonprofit National Center for Appropriate Technology.

(Learn more about what causes global warming.)

Farmers are also drawn to renewable energy because they "like being self-sufficient," said Teresa Bomhoff, rural-energy coordinator for the Iowa office of USDA Rural Development. "They see it as part of their patriotism to reduce dependence on foreign oil."

Bomhoff has gotten 423 applications for USDA's Rural Energy for America grants from Iowa farmers, compared with 10 applications in 2003.

From Waste to Gain

Of course U.S. farms come in an array of sizes, crops, and geographic and environmental profiles, so farmers need to tailor energy programs to their needs.

"There's not really an average American farm," said Ryan Stockwell, director of energy and agriculture for the sustainability nonprofit the Minnesota Project.

The Haubenschild Dairy may be a good model for farmers dreaming of energy independence, experts say. Located near Princeton, Minnesota, this family farm demonstrates the possibilities of farm-energy production.

In 1999, with the help of several large government grants, the Haubenschilds bought an anaerobic digester system that cost about U.S. $460,000. The system works by cutting off oxygen to a big vat of waste—in this case, cow manure—heating it at a constant temperature and allowing bacteria to decompose the manure into a mixture of combustible gas and odorless, environmentally friendly fertilizer. The gas runs an electricity-producing generator, and waste heat from the generator is used to keep the vat warm.

(Related: "Human Waste Used by 200 Million Farmers, Study Says.")

The big investment has paid off for the Haubenschilds. Electricity from the digester powers their dairy, plus 70 other households.

"They have a power purchase agreement with the local utility, and they've reduced their own fertilizer bills considerably," said the Minnesota Project's Ryan Stockwell.

Fewer than seven years after installing the digester, the Haubenschilds recouped their personal investment.

Another cost-saving benefit to installing a digester is selling digestate, the less-polluting manure byproduct that is ideal for gardens, Stockwell added.

"There Are Great Opportunities"

But what worked for the Haubenschild Dairy won't necessarily work for other farms, experts say.

"There's not any one best technology for this," said Leif Kindberg, farm-energy specialist with the National Center for Appropriate Technology.

The Haubenschild Dairy has a thousand head of cattle producing manure. A farm with fewer than 500 or so would have a much harder time breaking even on an anaerobic digester, Kindberg said. The Haubenschilds were also fortunate to have a local utility that was willing to buy their electricity.

Individual farms have to look at their own energy needs—as well as what resources they have available—and figure out what technologies make financial sense, he added.

For instance wind turbines can bring in as much as $6,000 a year per megawatt of electric capacity.

Even so some farms aren't right for producing energy for sale. But even these farms can still reap benefits, Kindberg said.

For instance, Bomhoff, the rural-energy coordinator, helped an Iowa farm buy a more efficient grain-drying system that saved $12,000 in energy expenses every year.

Farmers can also save money and fossil fuels by using solar cells to power electric fences and water pumps on remote parts of their land.

"These are all great opportunities," Kindberg said. "But one of the key aspects is figuring out whether, on your farm, a specific opportunity is really there."