Carbon-Sequestering Concrete: A “Geomimetic” Material

By Kiley Jacques

Concrete is the bedrock of the built environment. Its versatility, durability, and affordability make it the most widely used building material in the world, which means it is uniquely positioned to help advance the green building industry.

In recent years, efforts have been made to use concrete production as a means for sequestering carbon dioxide (CO2)—a major contributor to greenhouse gas emissions. Among the innovators shedding light on the idea is biomineralization expert Brent Constantz, Ph.D., who found inspiration in the formation and evolution of coral reefs. Their ability to calcify is integral to his research, which he describes as geo-mimetic—a reference to geological mineralization processes. “In biomimicking what corals do, we’re really trying to mimic, in some cases, how they can mineralize so rapidly, so prolifically to make the larg-est biological structures on the planet,” he explains.

Constantz’s company, Blue Planet, Ltd., makes carbon-negative concrete by taking CO2 from smoke stacks at Moss Landing (California’s largest power plant), running it through saltwater containing all of the minerals used in the making of coral reefs, and precipitating out the raw materials for concrete. The process removes nearly 90 percent of the CO2 and combines it with minerals in the water, resulting in limestone made of approximately 50 percent CO2 waste. According to Constantz, the use of Blue Planet aggregate is the most effective way to achieve carbon neutral and carbon negative concrete.

“At Blue Planet, we are capturing carbon dioxide at point-source emitters—places where you can go to capture large amounts of carbon dioxide, such as coal-fired power plants.” That CO2 is turned into car-bonate minerals, the constituents of limestone used in concrete. For every ton of CO2 used, a ton of build-ing material is made. The twofold benefit: sequestering of CO2 in the concrete that would have otherwise have gone into the atmosphere and offsetting the need for transported materials.

Contractors looking to meet green building standards can earn carbon credits with products made using biomimetic carbon capture and mineralization technology. Blue Planet’s commercial- and residential-grade aggregate (blocks and pavers); bagged concrete (found at Home Depot and Lowe’s stores worldwi-de); roofing granules; cool pigments; and CaCO3 powder (an alternative to titanim oxide white pigment) are now available. Of particular note are their high-solar-reflectance pigmented sands, which  are more powerful than Dupont’s titanim oxide white pigment—commonly used in cool roofing systems. (Their pigment mimics the crystalline properties of biominerals, which have an extremely high solar reflectance, reaching into the ultra red range.)

The transformation of CO2 to a calcium carbonate base for building not only reduces the fossil fuel use associated with conventional cement and concrete production, but it also has the power to revolutionize our approach to coal emissions.

Topics: Building Green, Certification / LEED, Sustainability Trends & Statistics, Sustainable Products

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