Managing animal waste is an ongoing challenge to the hog industry in eastern North Carolina. Ruptures in some hog farm waste lagoons have contaminated rivers. Spreading waste on fields as fertilizer sometimes results in extra nitrogen or phosphorus discharges, which can throw ecosystems out of whack. And the odor from farms often elicits nuisance complaints from neighbors. But after more than five years of research by NC State scientists, better ways to manage and utilize the waste might soon be at hand.

As part of a agreement in 2000 between the State and major hog producers, the University was charged with the responsibility of finding technologies that were both environmentally superior to the lagoon-and-spray system currently being used on most farms and economically feasible for farmers to implement. Dr. Mike Williams, who recently stepped down as director of NC State’s Animal and Poultry Waste Management Center (APWMC), coordinated the effort, spending almost every day in recent years contemplating hog waste and its impact on North Carolina. “I don’t think we’re currently in a crisis, but I know that systems now being used aren’t sustainable over the long term,” he says. Drawing on research being conducted at APWMC and on other ideas in academia and private industry, Williams and his advisory board winnowed more than 100 possible waste disposal systems into a handful that University scientists like Drs. Jeanne Koger and Phil Westerman could test and tweak to meet the state’s objectives.

A system devised by Koger, a researcher in the Department of Animal Science, and former NC State professor Dr. Theo van Kempen separates the solid and liquid waste with a conveyor belt and uses a furnace to gasify the feces. The gases released in the process are captured to help run the furnace, and the sterile, mineral-rich ash left behind can be used in fertilizer or animal feed, Koger says. “Recycling the waste to create value-added products is much better for the environment and the economy,” she says. As she and engineer Preston Burnette work to scale up the technology and develop a system to recycle the liquid waste as well, they also eye other uses for the furnace, such as destroying animal carcasses after an avian flu outbreak or bioterror incident.

Meanwhile, Westerman studied a system developed by a Canadian company using microbes in aerated filters to digest waste in ten-meter-diameter tanks. The system works, he says, but the energy needed to inject air into the filters to help the bacteria function wasn’t cost-effective. In fact, says Westerman, a biological and agricultural engineering professor who specializes in animal waste issues, several of the treatment processes tested by researchers have been studied in some form for years and were not previously adopted by farmers because of added cost. “Unfortunately, that still seems to be the situation,” he says.

The economics of waste disposal is a major consideration for North Carolina’s $1.5 billion hog industry. Although North Carolina is one of the top hog producers nationally, farmers don’t control the market enough to simply pass the capital and operating costs of a new technology on to consumers, says agricultural economics professor Dr. Michael Wohlgenant. Forcing producers to absorb the costs would be catastrophic for the industry, he says, and would ripple across the state economy. Models developed by Wohlgenant show that adopting a high-end system could cost the industry $485 million per year and eventually wipe out close to two-thirds of North Carolina’s hog farms as major producers move operations to states with less stringent regulations.

But Dr. Viney Aneja says changes will have to be made for the sake of human, as well as environmental, health. An air quality expert in the College of Physical and Mathematical Sciences, Aneja says hog waste lagoons release about 250 tons of ammonia into the state’s atmosphere every day. In addition to contributing to the farms’ odor problems, the ammonia reacts with other gases to create fine particulate matter, which can aggravate respiratory problems. NC State graduate students now take air samples four times a year at hog farms in Pitt and Jones counties to use in determining how the particles are formed. Aneja, who is coordinating a national workshop in June on hog farm emissions issues, also is beginning to examine air samples for other emissions, such as sulfur gas and volatile organic compounds. “It’s easy to fix the water quality issues that arise from waste lagoons, but there are no easy fixes for the air quality,” he says. “The emissions affect more than the ecosystem. They could ultimately have an effect on our health.”

After reviewing the data compiled by University researchers, Williams submitted his final recommendations to state officials in January. The industry and the state are now considering the benefits and consequences of upgrading disposal systems. Williams says the move is necessary in spite of the potential economic distress, and he plans to continue monitoring the situation. “Managing hog waste will be a critical issue for North Carolina for the foreseeable future,” he says. “The state cannot continue to be a sink for the nutrients produced by large-scale farms.”

For more information, please visit