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Friendly Methane
Tue May 27, 2003
Listen in RealAudio 
Hi, I'm Bryan Yeaton and this is The Weather Notebook's weekly segment on global climate
change. Curt Nickisch today tells us about closing a methane energy loop.
At the wastewater treatment plant for the city of Sioux Falls, Public Works Director Lyle
Johnson is standing alongside pipes that carry sewage into massive tanks.
LJ: We've got three primary digesters, and a secondary digester there. They each will hold
about 600,000 gallons of sludge. And it's very warm in here because the digesters are kept at
98 degrees.
At that temperature, bacteria in the tanks break down organic waste and produce methane. The
gas is then burned in boilers to heat the digesters. Excess methane drives generators that
power the rest of the plant.
Using methane from human wastewater for fuel is fairly common. But the enormous energy
potential of livestock waste is largely unexploited. The methane from pig waste alone in the
U.S. could power more than three million homes. Pat Tracy of Prime Technologies, for
instance, plans to make the technology a cornerstone of a new combined ethanol plant and
feedlot. First, corn is processed into the fuel additive ethanol. The by-product of ethanol
production, called distiller's grain, can be fed to livestock.
PT: We then take the distiller's grain into a closed feedlot, where we feed cattle on slatted
floors, capture that manure, turn that into methane gas, and that in turn is used to fire the
ethanol plant to cut our cost of natural gas.
Tracy hopes eventually harnessing methane from livestock waste will be commonplace in farms of
all sizes. That would be a sizable source of energy, with the added environmental benefit of
keeping the greenhouse gas from going into the atmosphere.
In Sioux Falls, I'm Curt Nickisch.
Our series on global climate change is funded by the New England Science Center Collaborative
and the Roy A. Hunt Foundation.
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