The issue with biofuels is that we can’t actually produce enough of them to support anything like current levels of aviation, at least not without substantially displacing food production.
The issue with chemical synthesis is that it’s quite expensive.
So there’s a possibility that we’ll end up using hydrogen still.
Ohh I don’t think that we could sustain current levels of aviation with biofuels, though without their use as an lead substitute in gasoline and progress in reducing natural meat production we might be able to, just that it’s a lot more likely than getting a very slow to change industry to rebuild every single airport, aircraft, and fuel transport with a more expensive and less capable alternative.
Most of the limitation on chemical synthesis is from my understanding that it definitionally requires more energy than it produces, and as such doesn’t make much sense when that primary energy comes from fossil fuels which you could then have used instead. I also suspect that the cost while very high will be a lot lower than the amount required to basically rebuild the entirety of aviation from scratch.
