http://www.balancednewsblog.com/2008/07/20/calera-cement-to-sequester-co2/ Left and Right, both sides get a fair shot. Wed, 17 Feb 2010 07:13:58 -0500 http://wordpress.org/?v=2.8.4 hourly 1 http://www.balancednewsblog.com/2008/07/20/calera-cement-to-sequester-co2/comment-page-1/#comment-325 Ulu Wed, 20 Aug 2008 17:36:42 +0000 http://www.balancednewsblog.com/?p=4056#comment-325 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. 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.

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