We were surprised to see this covered in Forbes Magazine, an information source for big investors.
"As the nation's coal-fired power plants work to create cleaner skies, they'll likely fill up landfills with millions more tons of potentially harmful ash. More than one-third of the ash generated at the country's hundreds of coal-fired plants is now recycled - mixed with cement to build highways or used to stabilize embankments, among other things."
"But in a process being used increasingly across the nation, chemicals are injected into plants' emissions to capture airborne pollutants. That, in turn, changes the composition of the ash and cuts its usefulness. It can't be used in cement, for example, because the interaction of the chemicals may keep the concrete from hardening." Are we thinking about bridge replacement and repair using coal ash as an amendment to concrete? Because if we are, we better think twice.
"That ash has to go somewhere - so it usually ends up in landfills, along with the rest of the unusable waste. "You're replacing an air problem with a land problem - a disposal problem," said Bruce Dockter, a research engineer with the Energy and Environmental Research Center at the University of North Dakota... And the chemicals added to clean up emissions - such as ammonia, lime and calcium hydroxide - make the ash worse, environmental groups say, because they take toxins such as mercury out of the air but leave higher levels of it in the ash."
Although the Forbes article is insightful, it stops short of explaining a potentially critical factor. Historially, coal combustion wastes rarely exhibit the characteristics of hazardous waste. However, if coal burning utilities and the so-called "clean coal plants" were required to meet air emissions standards protective of human health, fly ash produced by them could be regulated as hazardous waste due to the elevated levels of mercury that would result. We might suppose that any fly ash with hazardous characteristics due to heavy metal content would have to be sent to special and expensive waste fills or be treated at great cost.
But we would be wrong to assume that. USEPA made fly ash exempt from regulation as a hazardous waste far before the risks of mercury and lead exposure were well understood and before air emission limits on heavy metals were contemplated. Hold that thought.
There is another unintended consequence of making fly ash toxic. Reduced use of fly ash as a concrete amendment means more cement must be added to the mix, increasing the carbon emissions footprint per Kg of concrete used.
These two reasons together explain why the coal utility industry has been opposed to more stringent mercury emission standards and why even the lenient mercury emission standards recently recommended by EPA were scheduled to be phased in so very slowly. Were high levels of mercury found in commercially sold fly ash, you can bet that a can o' regulatory worms would be opened. So, nothing to see here, move along now.