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What Project Vesta proposes is to mine large volumes of a (usually) green mineral called olivine, crush it up, and spread the resulting green sand on beaches all over the world, especially in the tropics where the water is warmest. Tumbled in warm, fast-moving water, this green sand would rapidly weather, essentially undergoing millions of years of the natural carbonate-silicate cycle in a few months or years. It’s a little strange to think of turning our beaches green, but on reflection that isn’t a major objection. Papakōlea Beach in Hawaii is one of four beaches in the world that naturally features green olivine sand. And Project Vesta estimates that to offset all the world’s annual emissions, only 2% of the world’s shelf seas are needed. Logistically, the plan seems at least plausible. One ton of olivine applied in Vesta’s process removes around 1.25 tons of CO₂ from the atmosphere. Olivine is superabundant, making up about half of Earth’s upper mantle, and currently costs around $25/ton to mine. At greater mining scale, mining and crushing olivine could be done for around $7/ton. Add around $3/ton for transport and logistics and you still have 1.25 tons of CO₂ removed from the atmosphere for about $10, or $10.62 as the detailed Project Vesta model has it). The Vesta team admits that a full life cycle analysis would lose up to 6% of the CO₂ saved, due to mining, milling, and transport. Even so, that works out to around $9.04 per ton of CO₂ removed from the atmosphere and ocean.

If Project Vesta’s estimates are right, humanity would completely solve the problem of climate change. To my eyes, it seems dirt cheap compared to many other proposals to respond to climate change (YC estimates direct air capture costs are $94/ton), and it is feasible using only technology that exists today. Even the skeptics among us should be intrigued.

The dawn of the age of geoengineering

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