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Rationalista's avatar

Chemical Engineer and pilot here. I’m not sure ethanol has all that much to do with SAF- it behaves terribly at even moderate altitudes and causes all sorts of issues. Ethanol can be used for gasoline replacement in spark ignition engines on the ground, but for small piston plane engines ethanol additives are expressly prohibited because they cause vapor lock and damage to fuel bladders and hoses, valves and seals not designed for it.

Jet turbines need kerosene or other middle distillates, which are much more likely to be consistent with biodiesel that comes from esterification of soybean or palm oils and that isn’t the same as the process of fermenting corn to make ethanol. Ethanol or methanol can be used as esterification agents, but that is only a small part of the overall energy density in the final fuel.

Long story short, biologically based commercial SAF has more to do with oil seeds, but we already know from biodiesel that that can’t be economic and is already a major driver of deforestation in Asia. The only SAF that could ever work would have to come from the synfuel route using DAC and Nuclear hydrogen.

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Tom Smith's avatar

Burning hydrocarbons is the only (current) viable way of powering an airliner.

Widespread international travel is a possible way to avoid wars (we Brits are much less likely to war the Germans now we know them).

War is really bad for the environment.

Hence relax about decarbonising aviation focus on the low hanging fruit ... and remember there was about 36 years between the Wright Brothers and the first jet aircraft, another 10 to jet airliners.

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