Globe-scale carbon sequestration would increase demand for olivine massively. Would mining operations be able to scale appropriately without prices going through the roof?
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Edit-As to pricing, if olivine is a common byproduct of other activities and generally common in that sense then obtaining 1 ton of olivine is the cost to move it. Then they need to process and disburse it. That seems like a cheap process.
Edit2-the non-cheap part of this seems the dispersal. How long will it take to disperse all that olivine?
If for any reason ophiolites weren't enough, there's places at slow-spreading ridges where it's peridotite all the way from the ocean floor to the outer core, albeit expensive to mine.
In short, we would run out of CO2 before we run out of olivine.
For the moment, that’s a slight overestimate; we’re a little over 400ppm, and pre-Industrial levels were about 300ppm, so we “only” need to remove 1/4 (and we don’t really need to go back all the way to preindustrial levels, it was about 325ppm in 1970)
In general, the cost of mining, milling and grinding 1 ton of rock in large-scale mining, has been calculated to be about $7/ton. Applied to olivine, it proposed that it would be about $12/ton.
The good news is that for the initial olivine, we will attempt to utilize "tailing" piles, which are the removed rock from existing mines. It turns out that diamonds, nickel, chromite, and other commodities are found in olivine-rich rocks. And to get to them, they have to dig up massive amounts of olivine that just sits on the site in piles as "waste."
Those tailings piles are also where some of the real-world calculations for olivine dissolution rates come from. They even determined that some mines hosted in olivine-rich rocks actually more than offset their own CO2 emissions in this unintentional way.
The ideal set up for a beach project would be right on the coast (in a tropical area as temperature affects the speed of weathering), near the end of a railway that runs from an abandoned mine with tons of tailings piles.
To bring the planets atmospheric CO2 concentrations back to pre-industrial levels would likely require around 30-50 new olivine mines globally. The good news though is that olivine is extremely common, making up 80% of the mantle. Almost every country has olivine/dunite deposits, and so countries with cheap labor and lack of other viable export commodities would be ideal places to open mines, which would also help create jobs for them (and ones that actually help the planet).
Prices wouldn't go through the roof, because the demand isn't there at higher prices. A significantly higher price would make other methods of sequestration attractive instead.
