alt Hacker NewsA while ago (years ago?) I read something about how carbon capture is so energy intensive that it doesn’t really help much. Is that still true?
I guess if you powered it with green energy, that’d be a net positive?
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Yes, but in an indirect way. Direct carbon capture (DAC) is so energy intensive that it's only viable in places with 100% clean electricity, like Iceland. It's a non-starter in most countries.
However, places that have 100% clean electricity are often isolated. You need to ship in all equipment, which is made elsewhere, and fly in all personnel. This quickly adds up:
https://heimildin.is/grein/24581/climeworks-capture-fails-to...
Capturing carbon from the source, like a coal power plant, is much easier. But the capture rate is only 50% on average, so a coal power plant with carbon capture is still horrible while also ridiculously expensive, so it doesn't really make sense.
Of course, direct air capture of CO2 is extremely energy intense. You can only do it if you've built excessive renewable energy overproduction. And I mean unimaginable excessive.
We've emitted more than a trillion tons of CO2 since 1990. If we want to put just that back into the ground (pump it into old oil wells), the final storage will be several thousand cubic kilometers of high pressure CO2. Just the direct air capture will cost more than an Exawatt hour of renewable electricity (currently, humanity produces around 30 PWh of electricity per year from all sources).
You can use some tricks. Turning all agricultural waste, forestry waste and organic garbage into bio char (instead of letting it decompose on the fields or in compost facilities, which emits CO2) captures a few billion tons per year, but that's far more labor intense and requires a lot of automation work.