skip to main content

→ Top Stories:
Clean Power plan
Safe Chemicals

Scott Slesinger’s Blog

Coal Ash: Why it is better recycled than as a waste

Scott Slesinger

Posted February 13, 2014

, , , , ,
Share | | |

Thumbnail image for Dan River Coal Ash spill credit Appallachian Voices.jpgphoto credit: Dan River coal ash pollution courtesy of Appalachian Voices

EPA has announced that the two primary encapsulated uses of coal ash are safe, so recyclers have no legitimate remaining arguments to support their previous requests for a weak coal ash rule.

One of the big issues propagated by the coal burning utility industry is that regulating coal ash waste as a hazardous waste would hurt the market for recycling of coal ash.  Even some in the environmental community believe that if something is hazardous as a waste, it would be hazardous in a product. This sounds logical but happens not always to be the case. There is a reason waste can be much more harmful than the same chemical in a product: It is the same as chemotherapy drugs; important and safe when used correctly, but toxic when they are no longer used, so disposal must be done carefully.

The key to the safe use of coal ash is encapsulation.  Encapsulation is the technology that is used at EPA-regulated hazardous waste landfills to make sure that if the toxic waste gets wet, which it does, it is bound at the molecular level into an insoluble compound that will not allow the toxics elements to leach to contaminate underground water sources or surface waters. 

This is the same technology used in encapsulating fly ash and FGD sludge in concrete and wallboard.  Therefore, it was not a surprise to me that EPA found that the use of fly ash in concrete and wallboard is no more a threat than the raw materials it replaces. Even if coal ash used in construction is demolished, it still will not leach toxics, because even if pulverized, it is not broken down below the molecular level.

The EPA study, released February 7, 2014 is entitled "Methodology for Evaluating Encapsulated Beneficial Uses of Coal Combustion Residuals" and an accompanying document, "Coal Combustion Residual Beneficial Use Evaluation: Fly Ash Concrete and [flue gas desulfurization (FGD) Gypsum Wallboard," applies the new methodology to those practices.

The risk evaluation document concludes that "environmental releases of constituents of potential concern (COPC) from CCR fly ash concrete and FGD gypsum wallboard during use by the consumer are comparable to or lower than those from analogous non-CCR products, or are at or below relevant regulatory and health-based benchmarks for human and ecological receptors."

“Based on the conclusion of the analysis in this document stated above, and the available environmental and economic benefits, EPA supports the beneficial use of coal fly ash in concrete and FGD gypsum in wallboard." 

NRDC, as well as the Green Building Council, agrees that recycled fly ash in building materials is superior to alternatives.  Regulating the disposal of fly ash should raise the price of disposal and therefore encourage more companies to recycle fly ash. Such reuse will protect our air and water and lower greenhouse emissions by lowering the carbon inputs into cement. 

The coal ash recyclers should support EPA’s regulation of coal ash disposal instead of continuing down the road with the utilities.  The utilities are very happy with the present weak standards which, not surprisingly, led to the recent spill in North Carolina in the Dan River.  It is time these companies spent their money upgrading their facilities rather than lobbying Congress to keep Americans at risk from their unsafe practices.

Share | | |


Michael BerndtsonFeb 13 2014 05:00 PM

Is this issue for all coal combustion residuals (CCR)? According to an EPA FAQ, CCR includes flue gas desulfurization solids, fly ash, bottom ash, and slag. I believe potential future uses for each are different based on respective physical and chemical properties.

Just to be clear, this has nothing to do with toxic Chinese drywall, right?

Scott SlesingerFeb 13 2014 05:46 PM

EPA did not look at anything other than fly ash. Chinese drywall is not encapsulated which is why there off gases are emitted.

Peter CrownfieldFeb 14 2014 09:19 AM

I don't know much about the encapsulation, but I am concerned that by embedding hazardous waste in concrete or drywall, it will be released when sawed or when it is demolished for replacement. Those doing the work -- who may be homeowners who are completely unaware of the hazard -- and passers by will then be exposed to this very harmful material.

Michael BerndtsonFeb 14 2014 01:01 PM

I'm a little confused. Drywall consists chiefly of gypsum (>85%). The other stuff seems to be fillers, stiffeners, and reactants of some sort or another.

Gypsum is calcium sulfate - dihydrate. Flue gas desulfurization (FGD) is made during pollution control of coal combustion stack gases. The stack or flue gas is scrubbed with a water and calcium carbonate mixture (limestone) to remove sulfur products of combustion. FGD based gypsum is called synthetic gypsum. Reportedly, about 30 percent of the drywall is made with synthetic gypsum. Green buildings associations are supposedly cool with synthetic gypsum.

Fly ash is not the same as FGD. Do folks want to add fly ash into the drywall mix that makes up the remaining stuff that is not gypsum? I'm assuming the fly ash would be encapsulated in the gypsum. From reading things, fly ash has the consistency of pancake batter and is similar in handling as silt or clayey soil.

As you can tell I'm confused and need to read the EPA docs. Thanks and interesting stuff.

Ash HoleFeb 14 2014 04:20 PM

The #1 recycling option for fly ash is in concrete products. ~50% of fly ash is recycled in concrete and concrete-like products.
Bottom ash and slag are used as roofing granules and as lightweight aggregate (concrete block), think sand and gravel.
FGD sludge for drywall as long as it doesn't have mercury removal waste comingled.

Sawing FGD drywall is no more hazardous than virgin gypsum drywall. Same goes for fly ash and non fly ash concrete.

If you are doing ANY demolition without proper protective equipment, even as a homeowner, you are unaware of all of the public warnings on how stupid that is. If you are a contractor raising any dust for passerby, you are probably breaking the law.

Comments are closed for this post.


Switchboard is the staff blog of the Natural Resources Defense Council, the nation’s most effective environmental group. For more about our work, including in-depth policy documents, action alerts and ways you can contribute, visit

Feeds: Scott Slesinger’s blog

Feeds: Stay Plugged In