Comment by mytwocentsworth | Hacker News Reader

Comment by mytwocentsworth | Hacker News Reader

mytwocentsworth

The second paragraph of TFA passingly mentions liquid fuels, then fails to elaborate. A blockbuster point is thereby deprived of appropriate emphasis.

According to Wikipedia[1], "Electrofuels, also known as e-fuels or synthetic fuels, are a type of drop-in replacement fuel. They are manufactured using captured carbon dioxide or carbon monoxide, together with hydrogen obtained from sustainable electricity sources such as wind, solar and nuclear power."

I'm not against other approaches (such as vehicles using compressed hydrogen and fuel cells), but the implications of a drop-in replacement fuel are surely immense. As a short-term solution, synthetic fuels would allow us a slower and gentler transition away from our existing fleet of cars and trucks... and, where aircraft are concerned, e-fuels may even be a solid solution for the long term.

I'm sure there are challenges involved, so please no complaints that I'm expecting a miracle. But it disappoints me that so many discussions about hydrogen revolve around the same old topics... stuff like the energy losses associated with electrolysis, or the embrittlement of tanks used to store compressed hydrogen. With due respect, these are valid subjects... but it seems to me that HN readers (and Mr Gates) ought to find synthetic fuels a subject worthy of a great deal more ink. Darn! -- am I the only one who thinks this is exciting??

[1]https://en.wikipedia.org/wiki/Electrofuel

E-fuels don’t do anything other than make the original carbon consumption more efficient. Let’s say you have a coal power plant and capture the carbon to make e-fuel. You’ve made the coal more efficient, as you get the same amount of electricity + fuel, but it’s still carbon positive due to the laws of thermodynamics. E-fuels, while cool, aren’t that promising to me.

The assumption is both that the carbon is obtained via atmospheric capture and that the energy for fuel synthesis comes from renewables.

Ok well that's a bad assumption. Atmospheric capture is basically impossible (at scale) due to the size of the atmosphere and the density of carbon within it. Atmospheric capture is not something I'd bet the farm on.

Unless of course you have a source of carbon you can't yet replace effectively or at scale, or you extract the carbon from the environment[1]. the second option (and efuel in general) definitely isn't ready for primetime but it could be a viable option in the future to keep some classes of old tech running rather than expending effort building out new tech at massive scales when it could be used more effectively elsewhere.

[1] https://en.wikipedia.org/wiki/Carbon-neutral_fuel#Sources_of...

> Unless of course you have a source of carbon you can't yet replace effectively or at scale.

Wouldn't it be better to capture the carbon and sequester it? How is capturing the carbon and then burning it again (via e-fuel) good?

It's not that capturing carbon and then releasing it again is good. What's good is that the liquid fuel (made from green energy plus captured carbon) can be used in existing cars, ships and aircraft.

There's more info in the Wikipedia article I linked above. "In 2021, Audi announced that it was working on e-diesel and e-gasoline projects.

"By 2021, the European Federation for Transport and Environment advised the aviation sector was needing e-kerosene to be deployed as it could substantially reduce the climate impact of aviation."

Sorry, but I'm still not seeing how e-fuels are beneficial without violating the laws of thermodynamics. A plane is going to produce the same amount of CO2 whether kerosene or e-kerosene is used. The only way e-kerosene makes sense is if its production uses less CO2 than traditional oil extraction and refining. Given the relative simplicity of oil extraction, I find it hard to believe this will be the case. Maybe it makes sense in Europe where geopolitical considerations like energy independence outweigh strictly reducing CO2 emissions.

> The only way e-kerosene makes sense is if its production uses less CO2 than traditional oil extraction and refining.

Yes -- hold that thought! As noted above, e-fuel is made from green energy and captured CO2. So, net zero, more or less, after the fuel is burned. But traditional oil extraction doesn't begin by capturing CO2. So, burning that fuel is carbon positive.

Yes, but you're not answering why it's better to convert the captured CO2 into e-fuel rather than sequester it directly. My point is that converting to e-fuel instead of direct sequestration only makes sense if you can produce e-fuel from carbon more efficiently than you can extract and refine oil.

It’s better than digging up new carbon and releasing that into the air.

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