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By Jeff Horwich, Minnesota Public Radio
May 18, 2001
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Critics of President Bush's energy plan say it doesn't place enough emphasis on alternative or renewable sources of power. In Minnesota there may not be the sun of Arizona nor the wind of the Dakotas or California, but there are plenty of cows. A farm near Princeton is tapping the power of Minnesota's own natural gas.
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THE MAIN JOB of the 900 cows on the Haubenschild farm is producing milk. And they do it well, giving a total of 6,000 gallons a day. But anyone who's taken one deep breath of dairy farm air can tell these cows are equally busy producing something else.
Over the past 18 months, the Haubenschilds have discovered that the 22,000 gallons of "something else" these cows produce every day can not only meet the formidable electricity and heating needs of the farm, but can power 78 households too.
Tom Haubenschild, whose grandfather began the farm in 1953, had just recently bought into the family business in 1999 when the balloon-like lid first rose over his father's vision - the Haubenschild Digester.
"It's 30 feet wide, 14 feet deep, and 130 feet long, and it holds about 400,000 gallons of manure. And we maintain the temperature of that effluent at about 100 degrees, which is the optimal temperature of the bacteria for digestion," he points out proudly.
THERE'S A METHANE TO THE MADNESS
By putting a lid over the same bacteria that had naturally found a home in the farm's old manure lagoon, the Haubenschilds capture the methane produced by bacteriological digestion. Like a mini-Metrodome, the rubbery white lid is pushed taut by all the gas - three times as much gas, in fact, as even a giant dairy operation can use.
Enter Henry Fischer, business and community development manager for the East Central Energy Co-Op. "We agreed to purchase all the excess, whatever the digester would produce. We expected this to be a win-win for all of us, and it certainly has exceeded our expectations," Fischer says.
The Haubenschild farm is one of just 13 large farm digester projects in the country. The others include dairy farms and a few hog operations. But the Haubenschilds are the farthest north - an important distinction because of the 100-degree temperature needed by the bacteria.
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 every few minutes they have to step over the metal bars moving beneath their feet.
"These alley scrapers, 24 hours a day they're just slowly being scraped into the central pit right here," Haubenschild says.
POWER FROM THE PILE
The scrapers pick up everything in their path, and with 24 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 250,000-gallon pit.
The manure slurry flows to the mixing chamber, where it is stirred up before moving into the digester where the bacteria go to work producing gas. The mixing chamber sits below the deafening engine that burns the methane, creating ground-zero for the two forms of pollution associated with digester power - noise and odor.
Burning methane generates water and a small amount of carbon dioxide. The smell would be here anyway. 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 actually more effective as a fertilizer when spread on the Haubenschilds' cornfields.
THE BOTTOM LINE
At $355,000, setting up a digester project this size would scare off many farmers, even with the low- or no-interest loans available. But the Haubenschilds plan to pay it off in just five years.
The electricity they now generate themselves covers what would be a $2,000 monthly power bill for the farm, and they make another $4,000 a month selling surplus electricity to the power company. Digester power is dependable, churning out electricity 98 percent of the time compared with perhaps 25 percent for a wind turbine.
With just a few such experiments nationwide, no one is claiming the U.S. is on the verge of a bright new future built on the biological bounty of pigs and cows. But Tom Haubenschild is confident his family's digester demonstrates the untapped power of America's farms.
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