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Researcher explains 'superior' way to recycle coal ash, trap contaminants


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Researcher explains 'superior' way to recycle coal ash, trap contaminants

This is the second partin a series on coal ash recycling and the differences in how certain Southeast statesapproach beneficial reuse of the material. The third part will focus on beneficialreuse in Virginia, Georgia, South Carolina and Tennessee. The on ash recycling usesand challenges in North Carolina.

A team of researchers at a North Carolina university believethey have found a "superior" use for coal ash, which is often either buriedin ponds or landfills if it's not recycled for use in concrete.

"We made composite blocks," Kunigal Shivakumar, directorof the Center for Composite Materials Research at North Carolina Agricultural andTechnical State University in Greensboro, N.C., said in a recent phone interview.

These "blocks" essentially reverse the process in whicha macro product, coal, is broken down into a micro product, ash, once it is burnedto produce energy, the researcher explained.

"Obviously, the coal is a natural material," he said."It entraps a lot of soil, a lot of rock and so many materials."

The team discovered that through using these properties, theycould entrap much of the heavy metals in coal ash into the mold.

"They don't actually leach out any of these elements,"Shivakumar said.

"Ash is a very valuable resource," he added. "It'sa freely available resource. And actually, if you can manipulate the system suchas actually it becomes environmentally friendly, at the same time, it becomes avaluable product, that would be win-win."

Shivakumar noted that he and other researchers at the universitypreviously developed a product, known as Eco-Core, using fly ash as a fire-resistantcomposite material in the interior of U.S. Navy ships. This was viewed as a solutionto replacing more flammable polymer-based materials, but it has not made it intomass production.

The work, however, did not go unnoticed and Shivakumar receiveda call from state Sen. Trudy Wade shortly after the 2014 coal ash spill at Duke Energy Corp.'s retired Dan River plant in Rockingham County. The Republicansenator asked Shivakumar and his research team to look into how to make the materiala "value-added product."

"Although, actually, our previous technology was applicable… unfortunately we could not bring down the density and also the toughness of properties,"Shivakumar said. "That's when we started looking differently [at] how we couldmake this material at a lower density [while] at the same time it has the toughnessand all the mechanical properties and fire properties."

Shivakumar said the team even attended some community meetingsabout the state's coal ash problems.

"We heard the biggest problem was the leaking," hesaid, adding the team researched the properties in coal ash that contribute to theimpoundment leachate concerns.

The team, using ash from Duke's Belews Creek plant and other sites, discovered thatarsenic, selenium and occasionally vanadium and manganese were "leaching outvery significantly," Shivakumar said.

"The concrete [industry] is one of the large users of thiscoal ash. But when they put the coal ash to the concrete, it absolves moisture andweeps the water," he said. "My theory is it still has to leach out someof these toxic elements."

"This is a lot superior process and also the densities aremuch lower," Shivakumar said. "We are targeting this product mostly forthe building products and also for some of the infrastructure products, say forexample, road barriers and railway ties."

The team now plans to "scale up and hopefully commercialize,"Shivakumar said, adding it would cost approximately $2 million to fully demonstratethe product.

"This process works," he said. "We can take somepond ash and actually we should be able to make a value-added product."

"I think I see a lot more value [in these products] anda lot more return on investment," he said. "The hard part is actuallythe end users."

The researcher said he has talked to Duke Energy representativesand noted that the company also sent a team to visit the lab.

"Their bottom line is cost," Shivakumar said, notingthat right now the product is not economical, but it has the potential to be.