New Lagoon-closing method unveiled
By Sam Atkins
Published in News on August 13, 2004 1:58 PM
WHITAKERS -- Hog farmers planning to close their lagoons may have a new, more environmentally friendly way of doing so.
Instead of open pits, the lagoons could be converted into timberland, under a proposal unveiled Thursday at Hanor Farms in Nash County.
The idea began in 2000 and was originally designed for solid-waste landfills, according to Frank Humenik with the College of Agriculture and Life Sciences at North Carolina State University.
Researchers removed the liquid from two of the lagoons at the farm and filled it with soil. The surface was graded, and trees were then planted on the site.
Over time the trees will absorb the nutrients from the sludge in the bottom of the lagoon. The trees could also provide timber that could be harvested and enable other uses.
Mike Boyette, a Philip Morris professor at N.C. State University, said the sludge removed from the lagoons could be combined with shredded cotton stalks to produce mulch. Cotton stalks absorb three times their weight in moisture, are renewable and easily harvested, he said.
Statistics show that there are a large number of hog lagoons in North Carolina that may require closing. There are 1,700 inactive lagoons awaiting cleanup, and 4,500 more that are in use.
The method unveiled Thursday should prove to be cheaper and safer than the current method for closing lagoons, researchers say. But cost estimates are uncertain now.
Farmers now pump out the liquid, remove the residue, and usually transport the sludge from the lagoon to another site. The liquid is typically sprayed on the land near the hog farm. It costs about $43,000 per acre of lagoon surface to close a lagoon under this method.
Transporting the sludge contributes to that high cost. Transporting the sludge off-site also brings about some environmental concerns.
Around 300 trees were planted last December after the lagoon was filled at Hanor Farms. They were planted five feet underground, with one foot being in the sludge, said Mark Rice, extension specialist at N.C. State University. Wells have been placed to monitor the groundwater.
The trees are hybrid poplars, which cost $7.20 each. Researchers are planning to use different kinds of trees on a smaller lagoon at the farm.
"I think it's a great idea," said Thomas Andrews of Hanor Farms.
Researchers from N.C. State University have been working with Ecolotree Inc., an Iowa company that has patented technology for filling landfills and other contaminated sites.
The new alternative is still being evaluated by the N.C. Division of Water Quality, according to Tommy Cutts with the National Resources Conservation Service.
He said that closing a lagoon requires farmers to survey the site to determine the volume of liquid and sludge, do a waste analysis, identify where they plan to dispose of the waste, develop a lagoon-closure plan and nitrogen-management plan, and then remove all of the sludge and liquid.
The new process must be approved based on the environmental standards, be something that farmers can understand and perform technically, be something they want to do, and be affordable, said Cutts.