where can you buy green cement?

where can you buy green cement?

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 .

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 .

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.

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.

Green Cement is Carbon Neutral, Sequesters CO2 from Power Plants : CleanTechnica…

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.