Quote:
Originally Posted by PR_Glen
it's not, drywall companies have been using recycled coal ash in their mixtures for decades now. Far cheaper than gypsum too.
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You are misinformed. Coal ash can be very toxic, containing a slew of heavy metals (arsenic, mercury, lead, etc). Coal Ash is the collective term given to the byproducts of the combustion of coal. It can be divided into fly ash (AKA flue ash) - fine particulate residue, and bottom ash - the heavier byproduct that does not escape up the flue.
Apparently, degree of toxicity is largely dependent on the coal source - which makes sense.
While the byproducts can be used for industrial purposes, such as synthetic gypsum as you mentioned and concrete, thereby putting it to somewhat safer use than say a landfill where it can leach into groundwater, it may still present risks.
Here's a CNN article that does a pretty fair job of presenting both sides:
http://www.cnn.com/2009/TECH/03/20/r...ml?eref=rss_us