there is a typo in the article.

Aragonite (spelled correctly here) is a calcium and magnesium carbonate mineral. All the limestone in the sedimentary rock layers is likely to have been formed by long-ago carbon fixing by biology in the early days of life on earth. There must have been a lot more carbon dioxide in the atmosphere back in the precambrian era.

As an environmental geologist I've long thought this would be an auspicious way to lock up carbon (rather than injecting it in gaseous or liquid form back underground). Biomimicry principles promote doing this at normal environmental conditions rather than extreme temperatures or pressures or energy inputs.

I would rather this approach be used to scrub and remove carbon from the atmosphere rather than promote continued reliance on fossil fuel mining and combustion. There seem to be too many externalities with the mining process, (e.g. MTR or mountaintop removal and valley filling operations).

Side note: fly ash is a byproduct of coal combustion at midwestern powerplants, and most of it is landfilled and not reused. Remember the impoundment that breached and overwhemed the town in Tennessee last year? I don't know why fly ash would be scarce, and would hope that the fixed carbon slush from whatever process Calera is pursuing would have a higher value than this!

Thanks Tom for this great article. I can't wait for the superhero movie, maybe it'll include Spongebob?