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Comment by seiferteric | Hacker News Reader

This sounds like pure fantasy. A quick google search says the industry uses ~6.9*10^10 liters of jet fuel per year. Energy density of jet fuel is ~35 MJ/L. You would need at 100% efficient conversion ~76GW of continuous power to produce that. Realistically probably like 10x that... Current installed solar capacity is like 650GW world wide and it is not sunny all the time.

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> Current installed solar capacity is like 650GW world wide

Synthetic fuel is derived from hydrocarbons assembled from atmospheric C02. It can be powered by anything. Installed solar is irrelevant.

Where does the energy come from? CO2 is already "burned" you can't make an energetic hydrocarbon without providing energy, effectively "unburning"/reducing it.

> Where does the energy come from?

Anywhere. Nuclear. Wind. Waves. Initially, fossil fuels, because most energy comes from fossil fuels.

If nuclear is on the table, then okay maybe but it would take decades and many billions of $ to ramp up capacity. Solar was just an example, but all of the renewables will have the same problems I mentioned, there is no way you are going to get that scale of renewable capacity installed and running just for the aviation industry any time soon. And as for fossil fuels... what? I don't even understand, why would you use fossil fuels to extract CO2 out of the air, that makes no sense...

> it would take decades and many billions of $ to ramp up capacity.

As would re-tooling (a) the economy to be less reliant on travel or (b) the entire aviation fleet to be e.g. battery-electric. Change is expensive. We're comparing costs, and when I've done that, synethetic fuel is the best near-term, i.e. within 50 years, solution.

> why would you use fossil fuels to extract CO2 out of the air

Big plants (can) burn much cleaner than jet engines. (Also, it's an interim step.)

> > why would you use fossil fuels to extract CO2 out of the air

>Big plants (can) burn much cleaner than jet engines. (Also, it's an interim step.)

Please show me how you extract more CO2 out of the air by burning fossil fuels than you release.

And solar isn't "synthetic fuel". I don't think anyone is seriously recommending solar planes, at least not in the short term.

I was talking about using solar (as an example) as the energy input to produce synthetic fuel, not solar planes.

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