A RECENT CBS NEWS ITEM shares fascinating information about reducing global CO2 emissions. Ben Tracy and Analisa Novak give details January 16, 2023, in “Cement Industry Accounts for About 8% of CO2 Emissions. One Startup Seeks to Change That.”
Concrete. According to Wikipedia, “Concrete is the second-most-used substance in the world after water, and it is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined.”
Concrete is a composite material composed of fine and coarse aggregate (i.e., sand and gravel) bonded together with a fluid cement that hardens over time.
Cement. Typically, cement is produced through calcination of limestone. Its high-temperature (2700º Fahrenheit) reaction is CaCO3 → CaO + CO2 , calcium carbonate transformed into calcium oxide and carbon dioxide. Wikipedia describes, “Calcium oxide is a crucial ingredient in modern cement, and is also used as a chemical flux in smelting. Industrial calcination generally emits carbon dioxide (CO2), making it a major contributor to climate change.”
Magnitude of the Problem. Ben Tracy and Alisa Novak observe in CBS News that “the cement industry is responsible for about 8 percent of planet-warming carbon dioxide emissions—far more than global carbon emissions from aviation.”
“If the cement industry were a country,” Tracy and Novak say, “it would be the third-largest emitter of carbon dioxide in the world, after the U.S. and China.”
Calcium Silicate: No C. They report, “One startup seeks to change that. At the California-based company Brimstone, CEO Cody Finke and his team in Oakland have discovered a potentially game-changing solution: the world’s first carbon-negative cement, made from calcium silicate rocks.”
Calcium silicate, Ca2SiO4, is known primarily as an anticaking agent in food, for example, in table salt, and as an antiacid. It’s also commonly used as a safe alternative to asbestos for high-temperature insulation materials.
Its benefit in calcination making cement is evident: There’s no C, no carbon whatsoever, in the compound.
Of course, the combustion of coal, typically used in generating the required high temperature, has its own CO2 emissions. However, as a feedstock, calcium silicate can legitimately be called “carbon-neutral.”
Scaling Up. CBS News reports, “Brimstone is attempting to rapidly scale up its innovation thanks to big backers like Bill Gates’ Breakthrough Energy Ventures and Amazon’s Climate Pledge, claiming it will be cheaper and just as reliable as traditional cement.”
Is There Enough Calcium Silicate? “We’re just making the same thing from a different rock,” Brimstone’s Cody Finke told CBS News. What’s more, Tracy and Novak say, “According to Finke, calcium silicate rocks are about 200 times more abundant than limestone, which is traditionally used to make cement.”
Wikipedia notes that calcium silicate occurs naturally as the mineral larnite, named after Larne, Northern Ireland, where it was first identified in 1929. In cement chemist notation, it has come to be known as simply C2S, this time the C standing for cement, not carbon. ds
© Dennis Simanaitis, SimanaitisSays.com, 2023