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Capturing Carbon in Cement02-04-09 | News

Capturing Carbon in Cement

World Watch Institute estimates that unless cement plants become more efficient or transition to renewable energy sources, the industry ?EUR??,,????'?????<

In much of the world, replacing traditional wooden or earthen structures with concrete ?EUR??,,????'?????<

Alternatives have emerged this past year, however, that may redefine the future of cement. One company, California-based Calera Corp., claims to have found a way for cement production to absorb more carbon dioxide than it emits, acting as a vehicle for carbon capture and sequestration, or CCS.

Similar to how certain corals produce reefs by excreting dissolved calcium carbonate, or limestone, Calera sends carbon dioxide emissions through seawater to create a chalky carbonate byproduct. This cement substance is then mixed with aggregate and water to create concrete. Its production avoids the need to heat the cement materials in coal-fired kilns, while sequestering carbon throughout the process, the company says.

For every ton of cement produced, two-fifths of a ton of carbon dioxide is stored, according to founder Brent Constantz.

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Calera is not alone, however. California-based Carbon Sciences plans to mix cement with power-plant emissions and waste material from coal and steel production. Carbon Sense Solutions in Nova Scotia, Canada, redirects emissions from pre-cast concrete plants into new cement. And London-based Novacem says its magnesium silicate cement will absorb enough emissions to make it carbon negative. But Calera appears to be gaining the most attention. The company received interest from the U.S. Department of Energy last year ?EUR??,,????'?????<

But green building designers are searching for more dramatic changes in cement options. ?EUR??,,????'?????<

Alternative blends have included ash from coal-fired power plants, known as fly ash, and pozzolana, a volcanic ash. Although limited in their supply, these natural materials replace some of the fused minerals used in traditional cement, and therefore avoid the need to heat limestone to 1,450 degrees Celsius. The substitutes are becoming more common, mostly in continental Europe, according to the International Energy Agency.