BY: SWIKAR OLI
By the time “limestone and other ingredients [are heated] to 2,640 degrees F (1,450 degrees C) by burning fossil fuels” to create one ton of cement, concrete’s main component, another ton of carbon dioxide is released, sometimes more. Calera, a company that says it’s focused on “environmental sustainability,” wants to capture that release and put it to use–by making more concrete.
Crystallographer and founder of Calera Brent Constantz says, “for every ton of cement we make, we are sequestering half a ton of CO2.” The sequestered CO2 is converted into a calcium carbonate powder, which can be used as a building material. Calera tells the Scientific American it can use more than 90 percent of the CO2 it captures.
Though it’s still growing, Calera now “produces up to two tons of cement from carbon dioxide and industrial waste per day, sequestering about four-tenths of a ton of carbon dioxide in each ton of the material.”
The process owes corals for its idea, something Constantz studied while he was a graduate student. Corals, “or marine cement, which is produced by coral when making their shells and reefs, tak[e] the calcium and magnesium in seawater and us[e] it to form carbonates at normal temperatures and pressures.” Carbonate is a dissolved form of CO2. Wired describes the process, saying that “using the same process as corals, Calera captures carbon dioxide gas and dissolves it in water with other compounds to make calcium carbonate. Once the calcium carbonate is made, the carbon dioxide can be stored indefinitely.”
Using carbon capture to reduce emissions is not new. It involves CO2 being captured from polluters like fossil fuel plants and stored in a way that will not be released back into the atmosphere, like deep underground. But the novelty of Calera’s approach is that actually puts the CO2 to use.
Despite outside enthusiasm, builders aren’t exactly jumping on this new and seemingly uncertain technology. As Portland Cement Association’s Steven Kosmatka tells the Scientific American, “the construction industry is very conservative…It took PCA about 25 years to get the standards changed to allow five percent limestone [in the Portland cement mix]. So things move kind of slowly.” Calera had taken to mixing its product in Portland cement to ease into the market.
In the meantime, Carela could fix some of its nagging issues. The New York Times said in 2010 that “much of the skepticism about the project stems from the acid created in Calera’s chemical process. It has to find a way to dispose of it or neutralize it by adding alkaline materials, without creating more environmental problems or raising costs.” On a large scale, this could pose an issue, but when making concrete is the third-largest man-made CO2 pollutant in the world, creative solutions seem necessary, and Constanz seems confident of his Calera. He told the Scientific American, “We probably have the best carbon capture and storage technique there is by a long shot.”
Sources: theguardian.com, cxzhsl.com, calera.com, blogspot.ca
