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Scientists turn hog refuse into riches
September 17, 1996
Web posted at: 12:00 p.m. EDTFrom Correspondent Ann Kellan
ROSE HILL, North Carolina (CNN) -- Sewage waste disposal has long been a problem for municipalities and some businesses, but researchers are finding ways to convert the waste into a valuable resource.
The method has been in place at some municipal waste water treatment plants for some time, and North Carolina State University researchers are busy adapting it to businesses with a major waste disposal problem -- hog farms.
At one North Carolina hog farm, waste water is being sprayed onto trees as a fertilizer, much the same as it is at some municipal waste water treatment facilities.
"(The) trees don't distinguish between fertilizer from a bag and fertilizer from waste water," says NCSU's Doug Frederick.
At a treatment facility in Edenton, North Carolina, Frederick explained how the process works.
The waste stream is screened to remove large solids, and then it sits in a holding lagoon for several weeks so more solids settle to the bottom.
The water on top is disinfected, then sprayed onto 300 acres of trees. The site is monitored to make sure the ground water is not being harmed by run-offs.
There are similar systems where the waste water is sprayed onto grass, but trees provide several advantages. Forests, Frederick said, have a large root system, providing a large area for micro-organisms to flourish in the soil.
"And you're not dealing with a crop that has to be harvested multiple times during the year and so on," he said.
And there's another advantage -- the trees grow much faster.
"At age ten," Frederick says, indicating a stand of trees, "they are now at a point where they are very high quality trees for pulpwood, for making ... high quality paper."
And after they're cut for the first time, hardwoods sprout new trees from the stumps, so the next tree plantation starts itself.
There are limitations, of course. The system won't work in places where long-term subzero temperatures freeze the lagoons and stop the settling process. And it only makes sense in towns with plenty of affordable land for tree planting.
Whether it will work as well to clean up agricultural or industrial waste remains to be seen. The idea must be adapted to each application, but Frederick says the basic approach is to use natural processes to turn waste into wealth.
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