Hazy Regs Cloud Duke's Sulfur Emissions At Asheville Plant

Feb 24, 2015

The Sierra Club has accused Duke Energy of allowing unsafe levels of sulfur into the air in Asheville. A study by the group shows Duke's Asheville coal plant exceeds federal limits. Duke says it's complying with all standards. Both could be right, because of a dispute between states and the federal government.


Duke's Asheville Plant
Credit Duke Energy

Five years ago, the U.S. Environmental Protection Agency tightened sulfur limits, specifically to protect children and the elderly from the breathing problems airborne sulfur can cause.

To check the amount of sulfur emitting from Duke’s Asheville plant, the Sierra Club hired environmental compliance consultant Howard Gebhart of Air Resource Specialists. He took the company’s own data and plugged it into a model of Asheville’s meteorological conditions to see where the wind pushes the pollution. Northeast of the plant, Gebhart says, there’s way too much.

“These concentrations exceed the standard by roughly a factor of three or more, and they occur fairly frequently, about one out of every three or four days,” Gebhart said on a conference call with reporters last week.

Duke installed “scrubbers” to filter out most of the sulfur in 2005 and 2006, in response to the state’s Clean Smokestacks Act. But the report says, after a couple of years, the plant switched to a cheaper coal with more sulfur in it.

Duke spokeswoman Catherine Butler acknowledges that’s true.

“Higher sulfur coal provides a cost savings to our customers,” Butler says. “And so we balance a number of obligations including cost to our customers, and so that’s a big focus.”

Even with the switch, Butler says the company has stayed under state limits. The problem, she says, is the model Gebhart used.

“When you run the model—because it doesn’t have the same assumptions for various terrain—it just doesn’t work,” says Butler.

But, the EPA recommends that model for measuring sulfur emissions, and neither Duke nor regulators have pointed to problems in Gebhart’s work. And yet, regulators aren’t jumping at the report's findings either.

Ashley Featherstone at the Asheville Air Quality Agency agrees with Duke—the models can overestimate emissions.

“They tend to be conservative” and show worst-case scenarios, Featherstone says.

Featherstone says setting up monitors to actually measure emissions is far more accurate.

Asheville doesn’t have any monitors.

Without monitors and with modeling problems, Featherstone says North Carolina is still figuring out how to comply with the stricter sulfur limits the EPA set five years ago.

“They’re looking at whether or not they will determine compliance with modeling data or actual air pollution monitoring data. And so all of that is being worked out now,” says Featherstone.

In the meantime, the regulators are not enforcing the stricter, nearly five-year-old sulfur standard. Even if the Asheville coal plant exceeds the current federal sulfur limit, as Gebhart’s model shows, regulators would not crack down.

Part of this is routine. When the EPA creates a new standard, it sets the new emissions limit first. Then, it sets how states must enforce it, after receiving their feedback. But the “how’ in this case, has been a point of contention between the EPA and state regulators across the country—when to use modeling, how many monitors to have, and so forth—and the rule has been pushed back, currently until the middle of this year.