Coal Ash Products

The Good, The Bad, and The Truly Dirty

Pros and Cons of Recycling or Reusing Coal Ash

Whenever a story breaks about a newly discovered form of pollution, there is inevitably enormous outcry and many featured articles about what it is, how bad it is, the extent of the damage, and possible catastrophes. Then, after the investigative portion is done, comes the far more difficult question: What do we do now? In the case of the coal ash ponds along the Catawba, we know that we don’t want them there, but how can we best get rid of them? Much as we would wish them to, they will not just vanish into thin air. Over the years there have been many groups and organizations working on this problem, trying to figure out what to do with coal ash. Outlined below is a guide to some of these proposed recycling/reuse methods.  Some methods work, some don’t and some are outrageous. 


The Idea: Fly ash is a pozzolan- a material that makes concrete stronger. Ash (originally volcanic instead of manufactured) has been used since Roman times to build and strengthen buildings of all kinds, including landmarks like the Coliseum and the Pantheon. The idea is that fly ash is treated, excess carbon is burned off, and then it is safely reusable because any toxic materials are trapped inside the concrete matrix.

The Pros: If done properly, there is minimal leaching of toxic materials, and using fly ash in concrete benefits both the environment and construction companies. The use of fly ash in concrete reduces Carbon Dioxide emissions; because the production of Portland cement produces large amounts of CO2- reducing the amount of Portland cement used reduces the emissions of CO2 produced.

When the excess carbon in the fly ash is burned off, the energy produced goes back into the power plant, reducing the amount of fresh coal needed to produce power.

The use of local fly ash would be even more beneficial to the environment, reducing the amount of local pollution stored along our river and cutting down on the cost of transporting recycled fly ash from other locations. Concrete is currently being reused- ground up and used as aggregate in new concrete limiting its exposure to the outside environment.

The Cons: People have argued that the use of coal ash in concrete creates an argument for continuing to produce electricity via coal combustion. However, it is possible to use landfilled or impounded coal ash in conjunction with newly produced ash. Another argument is that the concrete matrix isn’t good enough at holding in toxins. But this claim doesn’t have much credence even with environmental groups. In a recent article by CNN, Earthjustice attorney Lisa Evans was quoted as saying "You want to make sure the harmful constituents don't leach out into land, air or water, and concrete seems to fit that bill."

Conclusion: Good- This does not mean that it should be accepted without any scrutiny but neither should it be dismissed. Currently this is one of the most widely accepted methods of recycling coal ash, endorsed by the LEED certification process and by the EPA.


Hungry Horse DamHungry Horse Dam in Montana was built using fly ash. Photo: US Bureau of Reclamation



The Idea: Chemically there is no difference between synthetic gypsum and natural gypsum, and it can therefore be used safely in industrial and agricultural uses.

For example, synthetic gypsum can be used to make wallboard. When dealing with agriculture, gypsum natural is used to enhance soil by providing nutrients needed to grow particular crops, like peanuts, which require a lot of calcium.

The Pros: It exists as a result of reactions removing dangerous things from the air. FGD (Flue Gas Desulfurization) scrubbers use limestone to react with sulfur in the gas produced by burning coal The gypsum itself that is produced is of a very high quality and its production reduces or eliminates the need to mine for gypsum.

The Cons: Can contain trace elements of pollutants such as heavy metals which latch onto the gypsum and stay with it. Gypsum is far more permeable than concrete and thus there is a higher potential for leaching of toxic materials into the outside environment. The imported Toxic wallboard from China is an example of this, though the gypsum used in the wallboard was mined.

There has also been talk of using gypsum in agriculture but even the American Coal Ash Association notes: “Not all FGD gypsum will be acceptable for agricultural use because of high chloride content and potential perception issues associated with heavy metals”. The EPA recommends that farmers consider a large number of questions before using gypsum on their crops, including how sensitive crops are to toxins, how pure the FGD gypsum is, and whether there is any chance that the gypsum can get into the groundwater.

Conclusion: Bad- Gypsum itself not a bad product or element, but when being used, the people using it in industry and especially in agriculture must be careful that it doesn’t contain trace elements like mercury or lead which might have latched on to it. Unlike concrete, gypsum is not a stable matrix in which such things can be held.

Structural Fill

The Idea: In areas where soils are not ideal for building, both road companies and other types of industry use coal ash as a filler to make the soil more even and stable.

The Pros: When used in wet soils coal ash can absorb some water, making the soil more stable.  

The Cons: The dams of the coal ash impoundments along the Catawba River have coal ash fill within the dams themselves. An independent contractor has analyzed these dams every five years, and almost all of the contractors say that the presence of the coal ash makes the dams susceptible to liquefaction (failure). A Japanese study called “Effective Reuse of Coal Ash as Civil Engineering Material” confirmed this finding that alone coal ash particles and powder had “almost no cohesion”

Conclusion: Bad- The use of ash in a structure to hold ash is mildly galling to the logical part of the brain; akin to using sand to hold in a sandbox. Spreading it out in farm structures or along roadways without keeping it encased can pollute the surrounding environment. Some states have regulations preventing coal ash from being used as fill when near the water table or in active fault zones.

Fly Ash

Photo: Processed Fly Ash

Fertilizer/Other Agricultural Uses

The Idea: Coal Combustion Waste can be used as filler in soil, as a fertilizer, and as fill for animal’s bedding (reducing bacteria). Overall, utilizing CCW’s so that they aren’t landfilled.

The Pros: Well, it’s not in a landfill anymore.

The Cons: Most studies which relate to fly ash use on farms focuses on structural benefits and pH levels of fly ash and not on the toxins which can result in bioaccumulation in food. Pesticides and other farm materials made from fly ash can also result in bioaccumulation.

Fly ash in farm use can cause toxic levels of arsenic and other dangerous materials within herbs and vegetables.  Scientific American wrote in an article on the subject:

“Crops grown in quantities of fly ash ranging from 5 to 20 percent of soil weight absorbed toxic metals, according to a study by Indiana State University researchers. When the amount of fly ash increased, the crops absorbed higher concentrations of arsenic and titanium. Basil and zucchini contained potentially toxic amounts of arsenic exceeding 6 parts per million. Concentrations of greater than 2 ppm had severe effects on vegetables, damaging the plants and decreasing production, wrote the scientists in a 2004 paper published in Environmental Geology.”

Conclusion: Truly Dirty- As a general rule, toxic materials + food do not mix. Until studies come out that can definitively prove that the addition of fly ash is not causing harm to crops and to the people that eat them, this claim remains a dubious one.

Mine Fill

The Idea: The idea behind using coal ash to fill in mines is that there are problems with acid water running out of mines and polluting the streams. Because coal ash tends to be alkaline (basic), it supposedly neutralizes the water.

The Pros: Companies that use this method claim that using coal ash for fill makes the mine aesthetically pleasing, reduces acid runoff, and increases tourism by filling in the ugly scars left by mining operations.

The Cons: The biggest case against using coal ash as mine fill was evidenced in Martin County, KY in 2000. A massive coal ash spill occurred, in what was then called one the worst environmental disaster in the southeast. The breach occurred when the ash broke into an old mine shaft beneath the dam, then flooded out of closed mine openings into local creeks. Mines are not stable places, and dumping loads of unconsolidated material into a mine is not all that different from dumping it into a landfill or surface impoundment- except the mine’s stability can’t be monitored as easily.

Conclusion: Truly Dirty- Far from actually helping the problem, this method just moves waste from one site to another, making it potentially even more dangerous. Some form of mine reclamation is needed, but at present, this is not the way to go.

Martin County 

Photo: Appalshop Film Sludge

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From the perspectives of 12 NC Riverkeepers, this report discusses how multiple environmental issues pose challenges in the pursuit of clean, plentiful water. Whether you are in North Carolina or downstream in South Carolina, read this report about the state of environmental enforcement.
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