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Power From Poop: Putting Manure to Use

Jessica Marshall, Discovery News

"This isn't new technology. It's not hard to implement," he added. "It's decades-old technology that's ready to go right now. We just haven't done it. We don't have incentives."

But now, the rising cost of energy and increasing drive to reduce greenhouse gases and generate renewable energy make this a better time than ever to consider this approach, Webber said.

"There are a lot of biofeedstocks that are receiving a lot of criticism," Webber told Discovery News. "This one seems controversy-free. It's a waste stream right now. It doesn't fall into the trap of competing with food."

"They paint a very rosy picture of biogas potential by considering all the animals in the country," said Christopher Weber of Carnegie Mellon University in Pittsburgh, Pa., who has studied greenhouse gas emissions from livestock.

Webber agrees that not all animals are kept in conditions where it would be easy to collect the manure. Large feedlots would be the best starting point. But his analysis provides an upper limit for what might be possible, he said.

Meat, especially red meat, has received recent attention as a less "green" diet choice than vegetables or fish because of the greenhouse gas emissions associated with its production, including from manure. Reducing the greenhouse gas emissions from manure improves the calculation, but it does not even the playing field, Weber said.

"It would do nothing about the carbon dioxide and nitrous oxide in the production of the grain to feed the animals, which is another large chunk of the greenhouse gases associated with red meat production," he said. Cows would continue to burp methane as part of their digestion, which is the largest source of methane in beef production.

"All in all, for grain-fed beef, I would think manure is responsible for a total of 20 percent of the life cycle emissions or so; a good start but certainly not enough to make beef on par with vegetables or fish in greenhouse gas production."

How Stuff Works: Why do cows produce methane?

Info on Biogas

Planet Green

Discovery Earth Live