Decommissioning swine waste lagoons
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Decommissioning swine waste lagoons

Mark Rice, assistant director, National Center for Manure and Animal Waste Management, and other College researchers are planting several tree species to see if some perform better than others in taking up nutrients from filled lagoons. (Photo by Becky Kirkland)

Ornate letter "T"
he use of lagoons to treat waste from North Carolina hog farms has generated considerable debate. Lagoon opponents say the structures produce odor and pose environmental risks, while others contend that a well-designed and managed lagoon is an acceptable waste treatment technology.

The controversy has generated research in the College of Agriculture and Life Sciences and elsewhere to develop technologies that could replace lagoons.

Yet what would become of North Carolina’s estimated 4,500 active lagoons, not to mention 1,700 inactive lagoons, if the state’s hog farmers were required to use other waste treatment technologies and abandon their lagoons?

Researchers from the College and Oregon State University are testing a method of decommissioning lagoons that may provide an economically and environmentally feasible alternative to the method now approved to close lagoons.

Almost all North Carolina swine farms use lagoons — large, earthen basins — to treat and store the waste produced by pigs. Farmers periodically spray lagoon liquid on nearby cropland.

Some of the waste settles to the lagoon bottom as sludge. The method now approved for lagoon closure calls for the liquid to be pumped out, while the sludge is then removed and spread on land. Plants grown on the land to which the sludge is applied take up and remove nutrients and other substances in the sludge that can pose environmental risks if not properly managed.

Photo of filled lagoon courtesy Craig Baird
Because lagoon liquid is typically sprayed on the land in the immediate vicinity of a hog farm, it’s usually necessary to transport sludge from a lagoon that is being closed to another site. Dr. Frank Humenik, coordinator of College waste-management programs, said transporting sludge is one reason it now costs about $43,000 per acre of lagoon surface to close a lagoon.

Humenik and other College researchers are working with Dr. Ronald Miner from Oregon State University and Ecolotree, an Iowa company that specializes in reclaiming landfills and other contaminated sites, to test an alternative method of decommissioning a lagoon. The work is funded by the College’s Animal and Poultry Waste Management Center and the North Carolina Pork Council.

The researchers have removed the liquid from two lagoons at a Hanor Farms site near Whitakers in Nash County and filled the lagoons with soil. The sludge was not removed. Monitoring wells have been installed at the site by the North Carolina Department of Environment and Natural Resources, Division of Water Quality, Groundwater Section, which has conducted initial groundwater testing.

Humenik said the two lagoons, one measuring 75 by 190 feet and the other 60 by 70 feet, have been inactive for several years. They were taken out of service when a larger lagoon was built. Several species of trees, including hybrid poplars bred for use on decommissioned landfills, were planted on the former lagoons.

Over time, Humenik said, the trees will take up and remove the sludge nutrients. The trees can provide harvestable wood and allow the land to be used for other activities in the future.

—Dave Caldwell

Field Day Planned

A field day is being planned for Aug. 12 at the Hanor Farms site. The event is tentatively scheduled to begin at 10 a.m. and conclude around noon.

Information will be available as plans are finalized on the Waste Management Programs Web site at

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