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Comment by throwaway_pdp09 | Hacker News Reader

Someone I think on a slashdot post calculated that we'd have to process about half the planet's atmosphere to get back theCO2, that is liquefy that much atmosphere to collect the CO2.

Then we'd have to put I guess hundreds of cubic kilometres of liquid co2 somewhere. I long ago lost any hope we will deal with it.

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You're missing the trick. If you've got "free" energy, you can reverse the process: combine the CO2 with water and turn it back into high density hydrocarbon solids that you can safely bury. Or, if you can pick the hydrocarbon, use them in construction.

Doesn't help with the amount of gas you'd need to process, but the storage part is doable.

200,000 years later: nuhumans "wooah, I just discovered that there are all these hydrocarbons buried in the ground. These would just be perfect for this industrial revolution we are having"

That would honestly be a huge upside to this approach. We've already extracted most of the easily accessible energy resources, so if our society fails, the next one will have a much harder time moving from agrarian to industrial.

Very good point, thanks.

Taking in mind absorption rate by plants, I wonder if you could do a controlled release in somewhere like a rainforest such that a minimal amount would make it back into the atmosphere and a majority would be taken in by trees and plants. Alternatively build large green houses and vertical farms and pump it directly into there.

Plants are not a sink for CO2, just a transition point. Any CO2 that is taken up by the plant gets released when it dies and decays.

Couldn't you bury the plants, the same as trees, sequestering the carbon underground?

You could do that. It is how most fossil fuels got underground in the first place. OTOH if you have the ability and available energy to bury all of that plant matter, maybe you could instead just convert the CO2 directly to carbonate and skip the part with the plants.

If you have the energy to distill a large proportion of the earth's atmosphere you have enough to crack the O2 from the C and not mess with plants etc.

True, and I had not considered that. I like the idea of growing more trees though.

Trees = good, I'm with you.

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