Utah legislator calls coal plants ‘giant air filters,’ but is he full of hot air?

Air coming out is cleaner than the air going in? The science says otherwise.

(Chris Samuels | The Salt Lake Tribune) Rep. Colin Jack, R-St. George, during a meeting of the House Public Utilities, Energy and Technology Committee at the Capitol, Monday, Jan. 29, 2024. Jack told colleagues that coal-fired power plants act like "giant air filters" and clean the air.

“When we’re talking even about the technologies we have today, in any of our coal plants, they all have bag houses and scrubbers, and the air that comes out with the steam is cleaner than the air that gets drawn into the fireboxes. So you can think of them, if you wish, as big giant air filters that make electricity.” – Rep. Colin Jack, R-St. George.

When St. George legislator Colin Jack made those remarks during floor debate last week, they left a few people scratching their heads.

As Jack was summarizing his bill, HB191, which adds new requirements for Rocky Mountain Power before it can close one of its two massive coal-fired power plants in Emery County, he sought to reassure his colleagues that coal power isn’t as bad as some say.

But the notion that coal plants actually clean the air? No one seems to want to back him on that.

The U.S. Energy Information Administration, a federal agency, lists several harmful emissions that come from coal combustion, including sulfur dioxide, nitrogen oxides, particulates and mercury. The scrubbers and bag houses reduce the amounts of those pollutants, but they don’t capture all of them.

All of Utah’s coal plants have bag houses and scrubbers. Still, according to data from the Utah Division of Air Quality, Rocky Mountain’s Hunter Power Plant was the state’s largest source of nitrogen oxide emissions in 2017, totaling 9,766 tons that year. The Intermountain Power Plant near Delta, a coal-fired facility that will shut down next year, was the second largest source of nitrogen oxide at 9,312 tons, followed by Rocky Mountain’s Huntington Power Plant with 5,927 tons.

The three plants were also the state’s largest source of sulfur dioxide emissions that year, combining to spew more than 8,276 tons of that pollutant. The facilities also release tons of other pollutants each year.

And none of the pollution controls on coal plants does anything to reduce carbon dioxide emissions, which are the single largest contributor to climate change. According to the Environmental Protection Agency, coal is responsible for 59% of U.S. greenhouse gas emissions from electricity sources, while producing 23% of the nation’s electricity.

A recent report from George Mason University, the Harvard School of Public Health and the University of Texas found that earlier studies have underestimated the deaths caused by coal emissions. Between 1999 and 2020, the researchers estimated, 460,000 deaths would not have occurred if there were no coal plant emissions.

There is one interpretation under which Jack’s reference could be technically correct. Coal plants often use a process called “flue gas recirculation” that pulls some exhaust gas into the firebox to help reduce pollutant emissions. In that respect, the air “drawn into the fireboxes” can have more pollutants than the gas leaving the stack, which has been filtered. But, overall, the plants do not emit cleaner air that they draw in.

Jack, an electrical engineer who works in the power industry, did not respond to Salt Lake Tribune requests to explain his comments.

“It’s absurd to suggest that coal plants somehow clean the air. If that were remotely the case, we would be looking into building coal plants on the Wasatch Front so we could run them during inversions,” said Logan Mitchell, a climate scientist and energy analyst for Utah Clean Energy, a nonprofit advocacy group.

“It’s concerning that legislators working on state energy policies might not understand the basic concept that coal plants produce harmful air pollutants,” Mitchell said. “... We know this, of course, with basic chemistry and decades of observations.”

“To compare a coal plant to an air filter is alarming and absurd,” added Luis Miranda, director of the Sierra Club’s Utah chapter. “The reality is that there is no such thing as clean coal, and data has shown that coal-burning power plants in Utah emit pollutants that harm our communities and our climate.”