Converting hog waste into energy: Not as neat and simple as it might sound

Public comment period ends Sunday on Optima TH’s air pollution permit for facility at Smithfield slaughterhouse


By Lisa Sorg, NC Policy Watch



Optima TH has applied for a state air quality permit to operate a major biogas facility at Smithfield Fresh Meats in the Bladen County town of Tar Heel. If approved, Optima TH could emit 24,500 to 40,800 tons of greenhouse gases each year.


Biogas, in the form of methane, would be collected from Smithfield’s wastewater treatment system, upgraded onsite at the Optima TH facility to meet natural gas standards, and then injected into a Piedmont Natural Gas pipeline.


From there, Duke Energy would use the methane to generate energy at several of its former coal-fired plants, including H.F. Lee in Goldsboro, Sutton in Wilmington, and the Smith Energy Complex near Hamlet, according to Utilities Commission documents.


The Optima TH project is part of a larger and controversial push by Smithfield Foods, major utilities and the state lawmakers to promote swine waste-to-energy projects in eastern North Carolina. Most of these projects are in low-income neighborhoods or communities of color.


However, unlike the other projects, Optima TH doesn’t use swine waste from Smithfield farms. Instead, the gas is produced from the wastewater treatment plant at the Smithfield slaughterhouse. It is among the world’s largest, killing 35,000 hogs per day.


Before and after their death, hogs generate a lot of waste: not just urine and feces, but blood and other products of rendering that are sent to Smithfield’s wastewater treatment plant.


Whether from wastewater treatment plants or swine farms, biogas systems generally send methane to a pipeline. Other gases derived from the process that are not useful in energy production, such as carbon dioxide and hydrogen sulfide, are burned off through a “flare.”

The flare is the primary emissions source.


In addition to greenhouse gases, the Optima TH facility would emit 170 tons of sulfur dioxide annually, as well as lesser amounts of carbon monoxide, particulate matter and other pollutants, according to the company’s permit application.


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