Turning CO2 Into Cement

A California company has succeeded in converting carbon dioxide emissions from a power plant into cement by bubbling the gas through seawater and producing calcium carbonate, which is then mixed with rock and water to create Portland cement. The technique not only offers a novel way to sequester carbon, but also bypasses the traditional cement manufacturing process, which in itself is the third largest source of greenhouse gas pollution in the U.S. Working at a California power plant, the company, Calera, essentially mimicked the process through which coral makes marine cement. By pumping the flue gases through sea water, Calera creates a slurry that is then dried by waste heat from the power plant. Calera says that for every ton of cement it produces, it sequesters a half-ton of carbon dioxide. The U.S. uses more than 122 million metric tons of cement a year and China uses nearly seven times as much — a vast potential market should the Calera technique become commercially feasible.