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173 points rbanffy | 1 comments | | HN request time: 0s | source
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VyseofArcadia ◴[] No.42127346[source]
Time scale is also something I want to know about. "Can I remove CO2 from the air and turn it into something valuable in a way that is cost effective?" is one question. Another question is, "Can I remove CO2 from the air and turn it into something valuable faster than a tree?"
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danbruc ◴[] No.42128010[source]
I have not thought about this too carefully so I might be overlooking something. With that out of the way, a quick search indicates that we burn about 90 % of gas, oil, and coal for one purpose or another. Let's round this and pretend we burn it all. To undo this we will essentially need the same amount of energy again that we got out of it when we burned it, we would need to use all the energy coming from fossil fuels to undo burning them. Conservation of energy essentially.

Which makes it obvious that the entire idea is pretty pointless, burn fossil fuels to generate energy to then use it to unburn fossil fuels. To do it with renewable energy, we still need the same capacity as the fossil fuel capacity and when we have that - ignoring issues like fluctuations in renewable sources - it makes more sense to just use the renewable sources directly instead of using them to undo burning fossil fuels.

If you want to use the process to pull carbon out of the atmosphere, then you first have to replace all fossil fuels with renewable ones, then you can use additional renewable capacity to remove carbon. Add additional 10 % capacity to the world energy capacity to undo one year of carbon emissions every decade, at least to a first approximation.

To come back to the initial question, you essentially need an industry the same order of magnitude as the fossil fuel industry to have a meaningful impact. Not going to happen anytime soon.

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thinkcontext ◴[] No.42130872[source]
> To undo this we will essentially need the same amount of energy again that we got out of it when we burned it

Amine based carbon capture at the smokestack captures about 90% of CO2 with a 20% energy penalty. There's a new natural gas turbine design that captures 100% at no energy penalty (Allam cycle).

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1. danbruc ◴[] No.42134331{3}[source]
Both those technologies do not undo the burning process, they just capture the carbon dioxide. Like putting a gigantic balloon on top of the smoke stack to trap the flue gases. The real problem here is what do you do with all your captured carbon dioxide? You are producing it at the same rate as you are consuming fossil fuels, for each tanker, pipeline, or train delivering fossil fuels, you will need an equally sized tanker, pipeline, or train transporting the carbon dioxide to some storage facility. For each well or mine extracting fossil fuels you need a equally sized hole in the ground to dump the carbon dioxide into.