> I've not heard of sustainable aviation fuel. Is it snake oil? Why wouldn't it just be "sustainable fuel" suitable for trains and automobiles?
Planes don't run on the same fuel as trains and automobiles.
The basic idea is pretty simple: it's all hydrocarbons. We traditionally use hydrocarbons grown as plants millions of years ago and stashed in the ground until we dig them up/pump out the ground. We don't put the carbon back in the ground -- it goes into the atmosphere mostly.
"Sustainable" fuels are the same thing except you grow the plants today.
Since plants growing today use carbon from the atmosphere, even when the fuel is burned like traditional fuel, you're not adding much net carbon to the atmosphere.
Everything else is mere details, such as: growing plants today is much more costly than digging up plant material from the Cambrian; the fuel has to have the same energy density as traditional fuels; it has to not gunge up the engine; etc.
Planes don't run on the same fuel as trains and automobiles. The basic idea is pretty simple: it's all hydrocarbons. We traditionally use hydrocarbons grown as plants millions of years ago and stashed in the ground until we dig them up/pump out the ground. We don't put the carbon back in the ground -- it goes into the atmosphere mostly.
"Sustainable" fuels are the same thing except you grow the plants today. Since plants growing today use carbon from the atmosphere, even when the fuel is burned like traditional fuel, you're not adding much net carbon to the atmosphere.
Everything else is mere details, such as: growing plants today is much more costly than digging up plant material from the Cambrian; the fuel has to have the same energy density as traditional fuels; it has to not gunge up the engine; etc.