Scientists create a mineral in the lab that captures carbon dioxide

[eppur_se_muova]

3. There have been several business ventures which have claimed ...

to trap CO2 using solutions of calcium hydroxide, thus forming calcium carbonate.

Where does this calcium hydroxide come from ?

Why, by thermal decomposition (with evolution of CO2) of naturally occurring calcium carbonate, of course ! Thus we have a very expensive, energy-intensive system for, in effect, transporting CO2 from one point on the surface of the earth to another, while producing more CO2 in the process.

I don't see much to convince me this process is very different. Our principal source of magnesium is seawater, from which it is precipitated by adding -- wait for it -- calcium hydroxide ! Made from, guess what, naturally occuring calcium carbonate !