Growing Greener Cement

Shared by Sheila A. Menzies
Tile Heritage Foundation
Here’s breaking news that could positively affect the world: green cement! Tile installation standards will have a real chance to become more environmentally friendly since the basis of all tile setting materials is cement.
Stanford University Professor Brent Constantz says he has invented a green cement that could eliminate the huge amounts of carbon dioxide spewed into the atmosphere by the manufacturers of the everyday cement currently used in concrete for buildings, roadways and bridges. His vision of eliminating a large source of the world's greenhouse CO2 has gained traction with both investors and environmentalists. Already backed by venture capital, Constantz's company, Calera Corp., is churning out small batches of cement at a pilot factory in Moss Landing, California.
The reality is that for every ton of ordinary cement, known as Portland cement, a ton of air-polluting carbon dioxide is released during production. Worldwide, 2.5 billion tons of cement are manufactured each year, creating about 5 percent of the Earth's CO2 emissions.
When Constantz learned about the high CO2 levels, he thought he could do better. He claims his new approach not only generates zero CO2, but has an added benefit of reducing the amount of CO2 that power plants emit by sequestering it inside the cement. To make traditional cement, limestone is heated to more than 1,000 degrees Celsius, which turns it into lime - the principal ingredient in Portland cement - and CO2, which is released into the air.
Constantz uses a different approach, the details of which remain secret pending publication of his patent. At his pilot factory, he outlines how the process works. His next door neighbor is Dynergy, one of the West's biggest and cleanest power plants that still billows carbon dioxide from its enormous smoke stacks every day. He takes that exhaust gas from Dynergy and bubbles it through seawater pumped from across the highway. The chemical process creates the key ingredient for his green cement and allows him to sequester a half ton of carbon dioxide from the smokestacks in every ton of cement he makes. He believes his cement would tackle global warming on two fronts: first by eliminating the need to heat limestone, which releases CO2; and second, by siphoning away harmful emissions from power plants, locking them into the cement. The same process can also be used to make an alternative to aggregate.
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