I didn’t know ultramafic rocks existed. Fascinating thing.

https://www.sciencedirect.com/science/article/pii/S0009254120301674

Engineered carbon mineralization in ultramafic rocks for CO2 removal from air: Review and new insights

buffy said:

I didn’t know ultramafic rocks existed. Fascinating thing.

https://www.sciencedirect.com/science/article/pii/S0009254120301674

Engineered carbon mineralization in ultramafic rocks for CO2 removal from air: Review and new insights

Concrete absorbs CO2.

There used to be a small company selling a concrete that was claimed to absorb extra CO2, but I haven’t heard of them for some time.

It could be it didn’t really work, or maybe the builders couldn’t monetise the CO2 absorption, so didn’t use it. Don’t know.

The Rev Dodgson said:

buffy said:

I didn’t know ultramafic rocks existed. Fascinating thing.

https://www.sciencedirect.com/science/article/pii/S0009254120301674

Engineered carbon mineralization in ultramafic rocks for CO2 removal from air: Review and new insights

Concrete absorbs CO2.

There used to be a small company selling a concrete that was claimed to absorb extra CO2, but I haven’t heard of them for some time.

It could be it didn’t really work, or maybe the builders couldn’t monetise the CO2 absorption, so didn’t use it. Don’t know.

Concrete and other CO2 absorbing rocks (such as in the Apollo capsule) are all made by heating carbonate to release CO2 first and then reabsorbing some of that CO2 back later. So only for small scale use such as in anaesthesia and in diving rebreathers.

Ultramafic rocks wouldn’t have that problem (or would they).

> Mining rocks for carbon-dioxide-removal CDR and solid storage may be cost-competitive with direct air capture using synthetic sorbents. Combined CO2 + solid storage via weathering of existing ultramafic tailings is relatively inexpensive

That seems feasible.

The net production of CO2 from any process requiring calcining adds to the CO2 in the atmosphere. Calcining of cement for making concrete accounts for a significant percentage of total anthropogenic CO2 emissions. The following is what you definitely don’t want to do on any sort of large scale.

> Mg-rich, Ca-bearing, highly reactive rocks include mantle peridotite and ultramafic intrusions.

Major ultramafic minerals include olivine, orthopyroxene (commonly enstatite), clinopyroxene (diopside) and garnet. Thes are oxides, not carbonates, and so are capable in an alkaline environment of absorbing and storing CO2.

Olivine weathers rapidly.

> most minerals in ultramafic and mafic rocks are relatively slow to react, with the exception of brucite and some fibrous serpentine. Thus, they focus on rapid carbonation of “labile Mg” contained in the latter two materials.

This graph is impressive

> Because the annual storage capacity of newly mined ultramafic tailings is small compared to human emissions, the question arises whether one could mine ultramafic rock for the purpose of creating fine-grained rock reactants for carbon dioxide capture.

The Rev Dodgson said:

Concrete absorbs CO2.

Only problem being that manufacturing the stuff is incredibly carbon intensive