Digesters will spread as scientists figure out ways to make them cheaper and more efficient, says C. Mike Williams, director of the Animal and Poultry Waste Management Center at North Carolina State University. The EPA already offers incentives and technical assistance to farmers nationwide to promote the expansion of digester systems.
"Farmers like the idea of using every bit of what comes off their farms,'' said Vujic, of Duke University as she walked near barns full of squealing hogs on Bryant's farm. "They can manage their waste and save money while doing it.''
Digesters cost more than a lagoon, so some corporate factory farms that dominate the dairy and hog industries are reluctant to convert, the EPA acknowledges. Bryant paid nothing to install the digester system. The university, the power company and Google will cover operating costs for 10 years. After that, Bryant will own and operate the system himself.
The Duke system is a pilot project that was expensive to design and test, Vujic said, but new versions will be cheaper. And because North Carolina farmers are no longer allowed to expand unless they convert lagoon-and-sprayfield systems to waste management systems — after Hurricane Floyd ruptured hog lagoons in North Carolina in 1999 — the new model offers a way to expand their farms and profits.
Bryant previously planted only low-value millet and fescue grass, which can better absorb high nitrogen in lagoon effluent. But because the digester system cleans wastewater and transforms nitrogen into usable forms, fields sprayed with the water are ideal for raising cash crops such as corn or wheat.
"It's a pretty good deal," Bryant said. "I'll be able to put in corn and wheat and beans, and I'll get more yield on less land."
It smells a lot better around the farm these days too. There's a faint whiff of manure, but nothing like the overwhelming and persistent stench of hog waste lagoons.
"People tell me the smell's a lot better now," Bryant said. "To tell you the truth, the smell never bothered me. I just love hogs.''
Graphic: Power-generating hogs