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John Michener's avatar

I am a strong supporter of the enhanced rock weathering approach, and nuclear explosives are a cost efficient means of breaking rock, but the efficiency of this seems highly dubious. We need the rock broken very fine and dispersed very widely or the neutralization removes all the local CO2 and stops. Dispersing sand and finer basalt will allow wide spread reactions in soil - and gradually release Iron, Magnesium, Calcium, and Phosporous into the soil A nuclear explosion is going to break a column of rock, depending upon yield, on the order of i hundreds of meters, where i may be less than one and is no more than a few. i is going to vary as the cube root of the yield of the blast. But broken rock does no good unless it is dispersed and exposed to flowing water, and to have a fast reaction rate it needs to be quite fine - and not covered by mud. If you are going to turn a seamount into rubble and then mine and grind the seamount into fine powder, it works, but the bulk of the work will not be the initial blast that rubbelizes the seamount. And you would still have to finely disperse the ground basalt.

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John Michener's avatar

Relevant weathering numbers: An Australian study of ground Basalt in farm soils had ~ 55% of the basalt in 10 micron powders consumed in 10 years, 99.9% of 1 micron powders were consumed in 10 years. 10 microns is too coarse for seawater neutralization - it settles too fast. 1 micron is probably finer than needed, at least in warmer waters. You want the basalt mostly weathered before it hits settles out of the surface waters. The weathering rate is highly temperature dependent and requires water, which slows down weathering in temperate soils.

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