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PRI's Environmental News Magazine


Air Date: Week of

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A few enterprising farmers are turning to a form of renewable energy they can find in great abundance on their farms. Minnesota Public Radio’s Jeff Horwich reports they’re tapping into the power of bovine natural gas.


CURWOOD: Let's face it, most people are squeamish when it comes to the question of manure, so it has long been overlooked as a source of energy. But these days, rising energy demand is giving prudery a run for its money, and a handful of farmers are already cashing in. Jeff Horwich of Minnesota Public Radio has this update, of the growing commerce and power made from animal waste, a different source of natural gas.

HORWICH: The main job of the 900 cows on the Haubenschild farm is producing milk, and they do it well, together giving 6,000 gallons a day. But anyone who's taken a deep breath of dairy farm air can tell that these cows are equally busy producing something else. Over the past 18 months, the Haubenschild's have found that the 22,000 gallons of something else these cows produce every day, can meet not only the formidable electricity and heating needs of their Princeton, Minnesota farm, but can power 78 households besides.

Tom Haubenschild, whose grandfather began the farm here in 1953, had just recently bought into the family business, in 1999, when the balloon-like lid first rose over the Haubenschild Digester.

HAUBENSCHILD: It's 30 feet wide, 14 feet deep, and 130 feet long, and holds about 400,000 gallons of manure. We maintain the temperature of that fluent at about 100 degrees, which is optimal level or temperature for the bacteria.

HORWICH: By putting a lid over the same bacteria that had naturally found a home in the farm's old manure lagoon, the Haubenschild's capture the methane produced by bacteriological digestion, and burn it for electricity. The technique has been around for decades and larger digesters have been adopted by some cities' sewage treatment facilities, but a recent wave of experiments is proving that the latest technology also makes digester power a realistic and sustainable option for farmers and animal feed lots.

The process starts in the barn, where the cows still do what cows do best- eat, sleep, and eat some more. The only change in the bovine routine is that, every few minutes, when they're not sleeping, the cows step over metal bars moving beneath their feet.

HAUBENSCHILD: These alley scrapers, 24 hours a day they're just slowly being scraped into the central pit right here.

HORWICH: The scrapers pick up everything in their path, and, with 20 gallons of waste per cow, per day, a stinking, roiling, growing pile of muck constantly slides toward the center of the barn. As the scrapers pass over a slot in the floor, the load drops over the edge and down into a quarter million gallon pit.

[sound of slopping]

HORWICH: The manure slurry flows to the mixing chamber, where it's stirred up before moving into the digester, where the bacteria go to work producing gas. Pipes take the methane to a deafening 125 kilowatt engine that burns it for electricity.

HAUBENSCHILD: Another by-product of this methane is the heat produced off the motor. We're capturing heat and we use it to heat our floors in the winter. We cut back substantially on our propane bills.

HORWICH: Burning methane generates water and small amounts of carbon and sulfur dioxide. The process certainly smells but digesters help to control over. All in all, it's much cleaner than the 50 tons of coal it would take to generate the same electricity each month. As an added bonus, the manure coming out of the digester is more effective as a fertilizer, when spread on the Haubenschild's cornfields. The bacteria leaves the nitrogen in the manure behind, in a mineralized form that is easier for plants to absorb.

The Haubenschild farm is one of about 30 such large farm digester projects in the country about equally split between hog and dairy operations. Kurt Roos manages a program for the Environmental Protection Agency that encourages new farm digesters. He says the technology has moved well beyond the novelty stage, and government investment, including support in the Bush energy plan, will help farmers face the biggest barrier.

ROOS: One of the things that's keeping it from expanding is just access to capital. Farms have a hard time borrowing money. And these things have a cost associated with them. But when you start to look at the environmental performance, understanding that a farm needs a waste management system, these types of systems make a fair amount of sense.

HORWICH: The Haubenschild's plan to break even on their $355,000 digester in just five years. The electricity they now generate themselves covers what would be a $2000 monthly power bill for the farm, and they make another $4000 a month selling extra electricity to their local power company. Kurt Roos says about 20 U.S. farms have projects in the works, and guesses there may be 2 to 3,000 more that would be good candidates for digester electricity. Even more power might come from smaller farms that pool their manure and process it at a shared digester.

With just a few such experiments nationwide, not even the technology's biggest boosters claim the U.S. is on the verge of a bright new future, built on the biological bounty of pigs and cows. But those already sold on digester power believe it may be one part of the diverse power supply of the future, sitting right under our noses, on America's farms.

For Living on Earth, I'm Jeff Horwich, in Isanti County, Minnesota.



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