Technical question here. I know they can make marine cement by, essentially, bubbling CO2 through sufficiently basic ocean water and letting insoluble calcium and magnesium carbonates form. I don't know the details further than that, but it's something like that. One problem is that, in order to negate the acidifying effects of the CO2, they have to add a base.I know that at least some desert soils (maybe most of them) are fairly alkaline, and contain a lot of calcium and magnesium and such. So could you meaningfully take a bunch of desert soil, put it in water, then bubble CO2 through it to make marine cement? Or would there be a simpler (or at least less water-intensive) method to collect the calcium and magnesium carbonate from desert soils for use as cement? Or is there some other broad aspect or angle of the problem that I'm missing?
Caliche is a hardened desert soil (rock) that is typically near the surface. I would think that you would end up digging a lot of desert to get much carbonates. There would be a large amount of heavy equipment use, lots of dust, and lots of lost habitat. Typically cement is produced by exposures of limestone that are ground down and converted to cement. I would think this would generally be a more economical and more environmentally friendly option. Since you apparently have a chemistry background, you may already know this, but cement is generally made by taking calcite or dolomite and heating it up to create lime / cement. This has been done since the Roman Empire. I have never heard of bubbling CO2 in calcium and magnesium carbonates. Are you suggesting that bubbling CO2 in ocean water will precipitate calcite? I think it would probably have the opposite effect and create more acidity which would tend to dissolve carbonates. Note: Ocean water is very basic. It is far from acidic and will almost certainly never become acidic. If you add a base to the desert soil, form a pile on the ocean floor, and bubble CO2 into it, you might precipitate some CO2 if the water is warm enough IMO. It would probably make more sense in most instances to simply use regular cement which is designed to form a very solid and strong structure. Carbonates will precipitate out of sea water in warm shallow water. Some of the beaches of the Bahamas are formed from precipitated carbonates called oolites.
