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Comment by alexose | Hacker News Reader

It's not that CO2 isn't valuable on its own, but that other carbon-containing molecules are even more valuable (especially when factoring in transportation costs). This helps prove out the technoeconomics of carbon capture.

Plus, if we wind down oil extraction, we'll need new processes to produce all the precursors we use for plastics. A cheap pathway to ethylene from captured CO2 and water would be huge.

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But that point drives right into this one: compressed CO2 is valuable. So the value of your carbon capture process is already very substantial after you've extracted the CO2 from the atmosphere. I mean I have a cylinder of CO2 under my kitchen counter right now for this reason.

So the question is, is this so valuable that it outweighs just selling that CO2 once you've pulled it out of the atmosphere?

Turning CO2 into a stable feed-stock seems to be an important part of it, given that as the article says, we need to be processing gigatons per year.

If we’re just using our captured CO2 to extract more fossil fuels to burn, thats not nearly as big a reduction in atmospheric CO2.

> A cheap pathway to ethylene from captured CO2 and water would be huge.

Is it considered cheap if the marginal cost of a PV MWh is close to zero ?

The energy costs are only part of the equation, though. Especially if your plan is to use excess renewable energy, the cost of your plant is a much bigger concern, because you can't run it all the time.

Marginal cost. And one might reasonably expect fixed costs too to keep dropping, altho not as spectacularly quickly.

How close to zero? 1 MWh at 100% efficiency is enough to convert 180 kg of CO2 to ethylene (note this only produces 51 kg ethylene). Annual excess carbon emissions are 36.8 trillion kg of CO2. At a cost of $0.10 per MWh, which is about 3-4 orders of magnitude lower than it currently is, that's still $20 Billion per year. A cheaper pathway is still going to save an incredible amount of money even if solar power got ridiculously cheap.

$20 Billion per year worldwide is chump change. But that's 3 or 4 orders of magnitude away eh ?

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