Green Bricks Made of Power Plant Coal Ash Move Closer to Market
Under development as a potential “green” alternative to clay bricks, bricks made from fly ash captured as waste by coal-fired power plants recently moved one step closer to marketplace feasibility with the finding that they are 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.
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.”
Once colored and shaped, the bricks are similar to their clay counterparts, both in appearance and in meeting or exceeding construction-material standards.
Liu used the first phase of his NSF support to make fly ash bricks more durable by engineering them to resist weather-related freezing and thawing. Now at work on the second phase, he is testing the brick material’s safety and preparing it for market.
While researchers need to study the bricks further to determine how the mercury absorption occurs and how tightly the metal is trapped, the new findings suggest that the bricks will not have a negative impact on indoor air quality.
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