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Making Cement The Way Coral Does it

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Building With Biomimicry

The creation of cement is an incredibly polluting process, but Stanford scientist Bret Constanz has found a way to mimic the way coral works, by creating cement from CO2 and water.

What a fascinating concept -- that corals might teach us to make eco-friendly building materials! What can we learn from them?

"Building reefs, the corals have developed an incredible ability to calcify. They’re the most prolific mineralizers on the planet. They form great structures like the Great Barrier Reef. In doing so, they’re able to make more mineral than any other organism we’ve ever seen. They’ve adapted specialized structures. 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 largest biological structures on the planet, like the Great Barrier Reef." Bret Constanz explains in this video.

For those of you who want a deeper scientific explanation of the process, the following is from

What’s the simplest way you could explain your process of taking CO2 and making concrete from it?

Brent Constanz: "There’s a natural interaction between CO2, which is a gas, and water. They come into equilibrium together and the CO2 is dissolved in water. The colder the water is, the more CO2 is dissolved into it. This forms another molecule, CO3, which we call carbonate. It’s the carbonate in carbonated water. The higher the concentration of CO2, the more carbonate you form. When we interact water with something with very high concentrations of CO2, like the flue gas of a power plant, we get much, much more CO2 dissolved in water to form carbonate.

That’s what Calera does. Across the street here at Moss Landing, there’s a 110 foot high absorber – it’s just a vertical carwash, which is spraying sea water through this big, vertical column. At the base of the column comes the flue gas from this power plant. It comes up from the base of the column, and it goes up and goes over the top. On its way out, with the sea water spraying through it, that same reaction occurs. The CO2 goes to CO3 as it dissolves in the water.

Sea water has calcium. When the calcium sees the carbonate, you form calcium carbonate, the solid. That’s what limestone is. That’s how corals form their shells. So that’s the basic process. The solids that form – it looks like milk – fall to the bottom and are separated. They’re dried out using the waste heat from the hot flue gas. There’s a way to trap the heat of the hot flue gas – it’s called a heat exchanger – so there’s no burning of fossil fuel to dry it out. That produces a powder in a spray dryer, which is akin to a machine making powdered milk. And that is the cement. The cement can be used to make aggregate, synthetic rock like synthetic limestone, or it can be kept dry as a cement and used in a concrete formulation."

--Bibi Farber

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