As published in the Nation's Building News and NAHB, there is a potential "green" brick being developed as an alternative to the traditional clay brick. These alternative "green" bricks are made from the fly ash captured as a waste product by coal-fired power plants and are said to be safer than some had expected.
Instead of leaching minute amounts of mercury as researchers had predicted, the bricks apparently do the reverse, pulling tiny amounts of the toxic metal out of the ambient air. Further research is needed to determine how the mercury absorption occurs and how tightly the metal is trapped, but it is believed that the bricks will not have a negative impact on indoor air quality and will meet or exceed construction-material standards. "Each year, roughly 25 million tons of fly ash from coal-fired plants are recycled, generally as additives in building materials such as concrete, but 45 million tons go to waste. Fly ash bricks both find a use for some of that waste and counter the environmental impact from the manufacture of standard bricks." "Manufacturing clay brick requires kilns fired to high temperatures," says Henry Liu, president of Freight Pipeline Company, who has been working on the alternative bricks since 2004 with support from the Small Business Innovation Research program of the National Science Foundation (NSF). "That wastes energy, pollutes air and generates greenhouse gases that contribute to global warming." By contrast, he says, "fly ash bricks are manufactured at room temperature. They conserve energy, cost less to manufacture and don't contribute to air pollution or global warming." Liu is testing the brick material's safety and preparing it for market. | 
Katharine Salzgeber - Denver EcoBroker
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Katherine - I read your post earlier today with interest. Isn't it amazing how much fly ash goes to waste each year? Hopefully as products such as Coal Ash Bricks are developed that number will decrease. I find it very interesting that fly ash bricks can be made at room temperature.
I took a field trip today to a jobsite where they were doing a pour for an Insulated Concrete Form basement. The contractor shared that the concrete was 30% Fly Ash. Thanks for the information.