State orders to close Duke Energy’s 32 coal ash ponds pose a 108 million-ton question: Are there better uses for ash than burying it in new holes in the ground?
The answer is a qualified “yes,” a state committee charged with probing that question learned Monday at UNC Charlotte.
Coal byproducts, including ash, can be used in products like wallboard, concrete and soil improvers. Research at UNCC and elsewhere shows new uses.
But technical aspects limit some applications and market economics hold back others. Much of Duke’s ash may end up in landfills.
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Duke recycles most of the synthetic gypsum it creates in scrubbing sulfur from power plant emissions. Charlotte concrete makers, however, complain that they have to import ash, a substitute for the cement ingredient, because Duke’s ash isn’t suitable.
This month Duke announced plans to ship ash from two power plants to reclaim land at open-pit clay mines in Chatham and Lee counties.
Structural fill, as the practice is called, has been around for decades. Yet it had fallen out of favor in recent years, other than a large project in Asheville, possibly because of the risks associated with ash.
The committee of the state Environmental Management Commission is charged with assessing whether state rules for “beneficial reuse” – recycling ash – adequately protect people and the environment. It will also evaluate new uses.
The committee is supposed to report by Jan. 15, as the General Assembly convenes. That’s less than a month after new federal rules that could affect its findings.
The Environmental Protection Agency will release the first federal rules on ash on Dec. 19. EPA’s key decision will be whether to rule that ash is hazardous waste, a finding that would vastly complicate its disposal.
John Daniels, a UNCC civil and environmental engineering professor who leads Duke’s ash advisory board, sees a world of uses for ash that also protect the environment.
The key, he said, is to align the ash’s characteristics, such as a tendency to leach metals into groundwater, with its end use.
“You could probably put a foot (thickness) of coal ash anywhere and have no impacts,” he said. “Seventy-five feet and you might have problems.”
UNCC researchers are developing a new use for ash in precast concrete, replacing the traditional Portland cement ingredient. They’re also working with a technique that can make ash shed water, reducing the odds that pollutants would reach groundwater.
N.C. State University’s Minerals Research Laboratory in Asheville found a way, a few years back, to turn ash and sludge into a lightweight aggregate that could be used in making concrete block.
Then the economy crashed. The product never reached production.