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Calera Corporation operates in the area of CO2 sequestration. They claim to have developed a nature-mimicing process that converts CO2, such as from a coal power plant, into cement. If company claims are true, they would be thus removing CO2 from the atmosphere in while making a product that usually produces a lot of CO2. The company claims to be in a position to help reverse human-caused global warming and ocean acidification. However, climate scientists and chemists have raised questions regarding the process and whether it actually sequesters carbon, or simply moves carbon release to a different manufacturing process step.
Their "cementitious material" is a kind of chalk which can be mixed Portland cement at up to 5%
- "For every ton of cement we make, we are sequestering half a ton of CO2. We probably have the best carbon capture and storage technique there is by a long shot." -- Brent Constantz, crystallographer and founder of Calera.
- "It is clearly a case of public misrepresentation: They claimed they could sequester CO2 with seawater and they cannot...
They claimed to be selling gold, but it turned out to be fool's gold." -- Ken Caldeira, Stanford climate and ocean scientist.
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How it Works
The Calera process essentially mimics marine cement, which is produced by coral when making their shells and reefs, taking the calcium and magnesium in seawater and using it to form carbonates at normal temperatures and pressures. "We are turning CO2 into carbonic acid and then making carbonate," Constantz says. "All we need is water and pollution."
The company employs spray dryers that utilize the heat in the flue gas to dry the slurry that results from mixing the water and pollution. "A gas-fired power plant is basically like attaching a jet engine to the ground," Constantz notes. "We use the waste heat of the flue gas. They're just shooting it up into the atmosphere anyway."
In essence, the company is making chalk, and that's the color of the resulting cement: snow white. Once dried, the Calera cement can be used as a replacement for the Portland cement that is typically blended with rock and other material to make the concrete in everything from roads to buildings.
Quoting from http://groups.google.com/group/climateintervention/browse_thread/thread/7b5ff4ee64ce759d It is well known that the dissolution of carbonate minerals in the ocean causes CO2 to be transferred from the atmosphere to the ocean through a process characterized by the net reaction
(1) CO2 + H2O + CaCO3 --> Ca2+ + 2HCO3-
A number of authors have discussed ways to accelerate these reactions to store carbon in the ocean, neutralize carbon acidity, or both (e.g. Rau, Kheshgi. Harvey, etc). The idea of diminishing atmospheric CO2 content by dissolving carbonate minerals is discussed in the IPCC Special Report on Carbon Capture and Storage which has been reviewed by many people including prominent marine chemists. Reaction (1) is a well established net reaction involving dissolution of carbonate minerals in the ocean.
It is also well known that the formation of carbonate minerals from seawater, such as in the formation of coral skeletons, drives a flux of CO2 from the ocean to the atmosphere, essentially driving reaction (1) in reverse:
(2) Ca2+ + 2HCO3- --> CO2 + H2O + CaCO3
Furthermore, precipitating carbonates from seawater tends to lower ocean pH and thus exacerbate the ocean acidification problem.
Against this background it is surprising to see the company Calera claiming to sequester carbon dioxide by forming carbonate minerals where the cations are taken from seawater -- trying to drive the above reaction in the opposite direction to what would diminish atmospheric CO2.
Unit costs as well as energy costs, e.g. cents/kw-h, including factors such as installation, maintenance, decommissioning; relative to other renewable technologies as well as relative to conventional energy products.
- CO2 sequestration rather than production.
- Cement fabrication
Founder: Brent Constantz
Company: Calera Corporation
The privately-held company was founded in 2007 and is based in Los Gatos, California.
In the News
- Global Warming > CO2 Sequestration >
Cement from CO2: A Concrete Cure for Global Warming? - While Calera's process of making calcium carbonate cement wouldn't eliminate all CO2 emissions, it would reverse that equation. "For every ton of cement we make, we are sequestering half a ton of CO2," says crystallographer Brent Constantz, founder of Calera. "We probably have the best carbon capture and storage technique there is by a long shot." (Scientific American; August 7, 2008)
See Discussion page
Brent Constantz: Founder