Green Cement is Carbon Neutral, Sequesters CO2 from Power Plants
New ideas for reducing CO2 seem to be popping up all the time. The latest scheme for getting rid of the greenhouse gas comes from Stanford Professor Brent Constanz. The Geological and Environmental Sciences Professor has invented a new type of cement that is carbon neutral—a huge innovation for a material whose production process normally spews vast amounts of CO2 into the atmosphere.
Not only is Constanz’s cement carbon neutral, but it also sequesters CO2 emitted from power plants.
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The details of the cement process are secret until it is patented, but Constanz reveals that it does eliminate the need to heat limestone, a major source of CO2 emissions.
In Constanz’s vision, the green cement factories are built next to power plants, and exhaust gas released from the power plants is bubbled through seawater. The resulting chemical process creates an important ingredient for the cement. It also sequesters a half ton of CO2 from the smokestacks for every ton of cement produced.
And the green cement will even be cost-effective—$100 a ton versus $110 for standard Portland cement.
If green cement goes mainstream, it will drastically reduce CO2 levels, as the cement manufacturing process currently produces 5 percent of the world’s CO2 emissions.
The faster green cement replaces regular cement, the better for our planet’s health.
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Avigadro - As previously mentioned this process pumps seawater into a holding tank and that is where the process takes place. As a side note I find it rather odd that a global warming skeptic bothers to even read a blog devoted to green technology, unless their only purpose for being here is to troll.
Tony - Just because you work in a cement plant in no way means you are an expert on the subject. The scientist who developed this process, Brent Constantz, has nearly 60 patents in various kinds of medical cement, which means he must be pretty knowledgeable in the ins and outs of how cement works. And as to whether its been tried, the company that has been set up to produce cement using this process already has a pilot plant in operation in Moss Landing (Monterey County), CA making small batches.
The only issues that have not been tackled yet regarding this process is whether it can be scaled up and whether the cement that is produced has the same strength and characteristics as the portland cement that is now used.
Calera’s cement is utter balderdash on so many levels - a couple of preliminary takes:
1) Where is the cement??? Calera appears to be making Ca/Mg carbonates via a biological path - ie. their cement is carbonate (magnesian calcite) skeletons - they are collecting the skeletons and drying the sludge. This will give a Ca/Mg carbonate powder akin to powdered chalk and limestone. None of these are cementitous (ie. preformed Ca/Mg carbonates will not set into a cement when combined with water) - unlike Portland cement.
2) Note that Calera is now saying that they will not offer a 100% replacement for Portland Cement, but rather a 50:50 blend. This clearly points to their “cement” simply being a filler - you can acheive the same (very poor results) by using powdered limestone or chalk.
3) Note that Calera has also emended their initial claim that their process captures one ton of CO2 for every ton of cement produced, to half a ton of CO2 capture. Stay tuned for more amendments.
4)Assuming (biological) capture of Ca and Mg from seawater as carbonates via Calera’s technology, one ton of carbonate cement would equate to at least 500 tons of seawater (at > 80% Ca/Mg capture efficiency)- or ca. 250-300 tons of desalination brine. So, to supply just US cement demand (ca. 100 million MT pa), you would need to process 50 billion cubic meters of seawater. The most economic method would be to piggyback the process onto desalination capacity, but even with projected desalination capacity increases, desalination brines could supply at most 6% of US cement demand. And, processing seawater for cement production alone is neither economic (Note: Portland cement sells at $100-120 per MT in the US) nor environmentally friendly.
5) The Calera process will generate a Ca/Mg-stripped brine rich in Na/K. Many studies have indicated the severe environmental impacts that such brines have when discharged into the ocean - so much so that regulations now dictate dilution of such brines, remote discharge or landfill.
6) In summary - Calera’s “cement” is a non-cementitous filler, whose production is non-scalable, uneconomic, and carries huge environmental consequences.
southstep의 생각…
Green Cement is Carbon Neutral, Sequesters CO2 from Power Plants : CleanTechnica…
Now that a couple of months have gone buy, has the professor patented the green cement invention and has the process been tested further?
I looked on the Calera Corp. website and all they have right now is a home page, which suggests that things are moving very slowly considering they were founded in 2007.
@Ulu,
My thoughts exactly.
I wrote a post on this for my blog.
“If we precipitate all of the Ca2+ and Mg2+ as carbonates (CaCO3 and MgCO3), sequestering 1 T of CO2 would require 360 T of sea water. Additionally, carbonate precipitation does not occur below a pH of ~10, whereas sea water has a pH of ~7.5-8.4 , which could be decreased by increasing the partial pressure of CO2. Increasing the pH of the solution to favor carbonate precipitation likely requires the use of a base, such as sodium hydroxide, NaOH.”
On the issue of blending, I think that the current ASTM standard allows 5% limestone (CaCO3) blend in Portland cement.
I hope (and believe) that Calera has overcome the obstacle of using 100s of tons of sea water to capture 1 T of CO2. Rather, I think that the source of calcium comes from alkaline materials such as clinker kiln dust added to the water. A patent talks about a similar process .
http://cleantechnica.com/2008/09/02/green-cement-is-carbon-neutral-sequesters-co2-from-power-plants/
where can you buy green cement?