There Is No Such Thing As Clean Coal
by John Laumer, Philadelphia on 08.28.07
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.
Via:: Forbes Image credit:: Fly Ash Pond Upgrade,
I know you are kidding about a waste problem. When they dig the coal out, they can easily fill the hole with the fly ash and hundred of millions of tons of garbage as well. We have all seen the underground disasters with mining coal on the news recently but the largest "clean coal", which mean "low sulphur", mines are huge strip mines out in the west that leave huge pits in the ground that are "begging" to be filled back in. You also cannot cry out of both sides of your mouth. First you cry because of the fly ash and then you cry because you may not have enough and cause other emmission problems. Using fly ash in concrete is an example of using a product that normally might go back into the landfill for a very useful purpose. And by the way, fly ash had nothing to do with the bridge collapsing in Minnesota and never will. Just another way to add a sentence to try and scare people. Limit your articles to facts or label them as fiction when they are written like this one. I have a scary story, how about we eliminate fly ash in concrete and treehugger picks up the bill for the material they need to replace it. Hows that for scary?
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I seem not to have communicated adequately James.
Most fly ash currently either is used in road construction as a landscape backfill or goes as you indicated back into mines. Only about a third actually goes into concrete.
The issue here is that if more mercury ends up in the fly ash instead of in the air that landscaping will no longer be legal and might become hazardous. Moreover, as a technicality, storage shipping and treatment would require haz waste permits and containers would have to meet hazwaste tech standards that would make the process unaffordable. This is not fear mongering - just fact - although it would be contingent on a case by case testing for whether a batch of ash displayed hazardous leaching characteristics, per the EPA rules.
Advocating the back hauling of all spent fly ash to the Wyoming mines in empty rail cars is not a bad idea. To make is shippable as a dry solid, though, it would first have to be dewatered in a fly ash pond or other similar process. The pending issue would be what to do with the extracted water if it had high mercury levels. Anything can be done for a dollar but one can't just ignore the issue by claiming that these points are only designed to engender fear.
James, that is a very simplistic retort. One big issue is that of transportation - if the fly ash can be reused in construction that will often be relatively local to its source (the power station), but if it's now going to be dumped back in the hole the coal that made it came from, it will have to be transported there.
Furthermore, in many cases those holes can only be filled up when coal extraction has finished, which might not be for a very long time. Another point is that the mines are not always simple holes in the ground, but often take the form of mountain removal, leaving no hole as such to be filled. One final point is that you support the use of fly ash in concrete, but the article makes the point that this is not possible when it is contaminated with chemicals - that is in fact the main point of the article.