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Comment by penneyd | Hacker News Reader

Any obvious downsides to this approach?

Mining the rocks, distributing the rocks to a central processing center, then shipping to the farms is all non-negligible and can easily be net positive emissions rather than sequestration.

It looks like they've considered that:

>Their model also incorporated the emissions costs of mining and then spreading this powdered rock over fields.

Of course, there's always a chance of errors in both how they estimated these emissions and how they estimated the amount of CO2 that will be removed.

> Transportation. Detailed transport analyses (based on UK road and rail networks) were undertaken to calculate distance costs and CO2 emissions for the distribution of rock dust from source areas to croplands. We used the GLiM database for the UK distribution of basalt deposits and the 2019 land cover map (Supplementary Information) to calculate transportation distances, cost (£ t−1 rock dust km−1) and emissions (tCO2 km−1) from potential local rock sources to cropland areas, together with UK road and rail transport networks. Spatial analysis was undertaken with least-cost path algorithms from the ArcGIS software.

Yea, it sounds like the model took this into the account, maybe the assumption that rock sourcing could rely on mines within the UK. If so, given the size of the UK, if the majority of transportation is by train and EV over UK distances, this might not be an issue.

Might need to be studied in different regions to determine whether there are any detrimental effects. It looks like it might alter the soil pH which could affect crops.

Sounds promising though.

Do rock minerals capture more oxigen than carbon?

They are mostly already oxidized.

And it wouldn't matter too much (within reason): we have vastly more O2 in the atmosphere than CO2 we want to get rid of.

The CO2 is at <0.05% concentration. O2 is at >21%.

It costs a lot of money.

Nickel pollution.

Also, inevitably running out of rocks.

Can somebody who knows about rocks weigh in here? I was under the assumption that pretty much the whole Earth crust was made of rocks, and that we’d run out of virtually any resource before we run out of rocks.

Basalt is extremely common, its not something that anyone will run out of.

We may run out of basalt sources that are close enough to farmland it can be spread on, but it would take a while. And trains would change the economics.

I'd imagine the types of rocks would matter. There are also a lot of ores that should remain in the ground, and not pulverized and spread, contaminating water and soil.

All the oceanic crust is made of basalt, so approximately 2/3 of the planet is covered by several miles of it. Unfortunately mining oceanic crust is impractical, for obvious reasons. However some oceanic crust got trapped between mountain ranges during continental collision, forming ophiolites. These can be suitable mining sites, together with LIPs (large igneous provinces) and the rocks of some shoshonitic (K-rich) basalt volcanoes.

Rock is not a scarce resource. The planet is literally made of it.

We're all just pond scum on a ball of molten iron.

Yeah, but it isn't an infinite resource. Eventually, I meant, inevitably, I wrote.

Nothing is infinite. For the purposes of grinding basalt rock to sprinkle on farms, it is essentially sufficiently abundant that it doesn't matter.

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