Calera Cement to Sequester CO2?
Calera cement, funded by Vinod Khosla, which would take CO2 from the air to make cement and contour crafting which is a technology for printing buildings to speed up construction by 100 times
could be used to build new cities, dams, wind turbines and airports and many other useful cement construction as productive carbon sequestering. It would be possible to simply build our way out of any CO2 issues. Carbon taxes or credits for removing CO2 ($25-100/ton in Europe) such as those proposed by Al Gore could make Calera cement virtually free for builders.
Converting the world cement industry to cement that removes CO2 instead of adds it would be a reduction 5 billion tons of CO2/year. The entire US production of CO2 is now 6 billion tons. The Al Gore proposal of de-carbonizing all US electricity generations was a plant to remove 2.4 billion tons of CO2 generation per year.
There was 2.35 billion tons of cement used in 2007 and demand is increasing at 130 million tons per year. 1.4 billion tons of cement produced and used in China is 2007.
Cement production makes between 1 to 1.25 tons of CO2 per year
Calera, a Vinod Khosla funded company, is starting up a pilot plant for a new type of cement and process that would remove that 1 ton of CO2 from the air to make the 1 ton of cement. The plan is have 100 plant producing up to 1 billion tons of the new cement by 2015.
CO2 emissions are 27 billion tons per year worldwide.
Various goals for avoiding climate change suggest reducing those emissions by 7 billion tons/year or more aggressively to have the current level.
An accelerated conversion of all cement production to a successful Calera process by 2015 would be 3.4 billion tons of cement in 2015 under normal growth. Increasing cement construction using contour crafting and the new cement and making more buildings and other objects so that usage is 10-40 billion tons/year instead of 4 billion tons per year (under normal growth) in 2020 would be a major form of productive carbon sequestering. Productive in that the buildings made of cement now holding carbon would be useful for economic enterprise.
The World trade center used 955,000 tons of cement and 200,000 tons of steel and had 10 million square feet of space.
The world commercial building business is a trillion dollar industry making billions of square feet each year.
Shanghai had 3000 buildings over 24 meters (12 stories) high by 2000 and a hundred over 100 meters and there has been a lot more construction since then.
New 5-7 MW and larger wind turbines are over 120 meters tall and use hundreds of tons of cement each.
There is also demand for hundreds of airports.
10.8 million tons of cement used for the Three Gorges Dam.
Source: Next Big Future.
Posted in: environment, science, technology
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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 (a 100% CO2 cement!), 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.
August 20th, 2008