It was the plumes of steam coming off his compost piles that got Gary Teague thinking about energy.
Oct. 12FORT MORGAN, Colo. It was the plumes of steam coming off his compost piles that got Gary Teague thinking about energy.
Couldn't there be a way, the cattle feedlot operator wondered, to capture and use the natural heat generated in the compost?
There is, Teague discovered. Now, he's taking it several steps further in building what will become the nation's largest anaerobic digester.
Think of it as composting on a big scale, with plenty of energy and environmental benefits.
At peak production after several years of phased development, Teague's $7 million system near Fort Morgan could generate enough electricity to serve more than 5,000 people. The process also will put tons of waste into useful service and reduce feedlot odors.
Some 40 anaerobic digesters, or ADs, now operate in the United States, chiefly by using livestock manure to produce methane, which in turn is used as a fuel in small electric generators.
Teague has plenty of manure. Each of his feedlot's 28,000 cattle produces about 10 pounds a day.
But what sets Teague's AD project apart from all the others is the addition of several other energy-rich feedstocks.
The manure will be complemented with byproducts from a Fort Morgan cheese factory, spilled milk from dairies, wood chips, spent mash from breweries, and even some waste ice cream scraped off the floors of a Denver dairy-products manufacturer.
Throw it all in a big stainless steel tank, mix well, and wait for bacteria to break down the wastes into methane, carbon dioxide and water.
Teague's project is no slam dunk. He's using a new technology modular tanks instead of the conventional covered pits that promises better efficiency but is expected to have plenty of kinks to work out.
And like other AD energy producers, Teague will need to negotiate a price for the electricity he sells to his local utilities, Morgan County Rural Electric Association and Tri-State Generation.
Utilities typically offer AD producers a wholesale rate of 3 to 4 cents per kilowatt-hour, less than half the 8 to 10 cents that Teague must pay for power he purchases from the grid. The disparity between the wholesale rate Teague might receive and the retail rate that he pays makes the economics tenuous until he produces power on a large scale.
In several years, and if everything works right, Teague might generate annual income of about $90,000 in electricity sales from each of the 12 to 14 modules he's planning to build.
Teague will start with one module, then use cash flow from electric sales to pay for additional units. He expects to produce power by January.
As energy producers, anaerobic digesters never will compete with huge power generators such as coal, natural gas and wind.
But ADs can help solve agricultural odor and waste problems with the fringe benefit of producing electricity for ever-growing power needs.
"There is a tremendous explosion of interest in this area," said Ralph Overend, a biomass energy researcher at the Golden-based National Renewable Energy Laboratory. "It's been on a slow curve, but it has really caught on during the past year." Driving the interest, Overend said, is increasing regulation of livestock waste streams, higher energy prices and concerns about global warming.
Anaerobic digesters help in each of the three areas:
State and federal regulations prohibit excessive discharge of livestock manure that can leach into streams and groundwater. ADs provide a mechanism to break the waste down and limit the disposal problem.
Colorado has a November ballot proposal to require utilities to provide 10 percent of power from renewable sources, and several states have enacted similar measures. The electricity produced from ADs helps supply the demand for renewable energy.
Methane vented into the atmosphere has 20 times the damaging greenhouse gas effect as carbon dioxide. Burning methane instead of allowing it to dissipate in the atmosphere helps reduce suspected impact on global warming.
"When you consider how many thousands of farms there are in the United States, each one of them could have something like this," said Ed Lewis, senior deputy director of the Colorado Office of Energy Management and Conservation. "Environmentally, it's a really wise decision and you've got the bonus of electrical production." The state energy office recently held a workshop on ADs that attracted 70 participants, and is providing the $125,000 cost of Teague's first digester tank. Additional costs for generators and other equipment will bring the cost per module up to about $500,000.
Teague doesn't consider himself an environmentalist. His first concern is making his system work efficiently and turning a modest profit.
But even after 10 years of producing compost from cow manure, Teague still expresses wonder at the agricultural alchemy that turns dung to beneficial uses.
On a recent fall morning, he picked up a handful of freshly made compost and took a deep whiff.
"Ah, it's got a nice earthy smell," he said. "We're taking a really nasty, smelly product and making something good out of it. That's a nice feeling."
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