[losteric]

Why is that an absolute? Can't biofuel sources be refined into jet fuel?

I understand that subsidies currently create perverse incentives in that industry, but I struggle to see why bioengineered carbon-neutral jet fuel is fundamentally not viable. That thinking seems very closed-minded.

[CalRobert]

Biofuels have been a disaster inasmuch as we've destroyed enormous amounts of rainforest to grow them, releasing quite a bit of carbon in the process (and destroying wildlife habitat, of course)

[losteric]

That'd not an argument that carbon-neutral supersonic jets are impossible and should be abandoned.

Biofuels doesn't necessarily mean subsidized corn fields... for example, algae and bacteria grown under specialized LEDs powered by renewable energy are another path forward.

Perfect is the enemy of the good. We can research supersonic jets in addition to better electric storage and propulsion systems.

[CalRobert]

That's great if we have the algae and bacteria. Right now we don't seem to. Maybe we should invest the money there.

In theory, you can power a big car on responsibly sourced fuel. In reality, selling millions of big cars is a huge problem, because of course people will understandably put in the cheap, ubiquitous fuel for which they're not covering externalities.

[worldsayshi]

> Perfect is the enemy of the good.

This saying is not suitable here because unsustainable technology isn't good. It's simply not worth the cost and we are borrowing from the future.

If the venture would be unprofitable up until the point when it would be sustainable would we still push money into it?

I say we should treat any venture that is unsustainable the same way we treat those that are unprofitable. But we don't. We allow unsustainable ventures to carry on without ever becoming sustainable. Which means that it is constantly borrowing (stealing) means from everyone else.

[worldsayshi]

In my mind the most viable way to make air travel sustainable is to use synthetic fuels produced with commercialised fusion power and atmospheric greenhouse gases as input.

It sounds very sci fi and I'm not sure it would even work on a napkin calculation produced by a thermodynamics professor.

[loeg]

Sure; it's not an unreasonable approach for making such travel carbon neutral; the idea being you're sequestering parity amounts of carbon via the atmospheric gases -> fuel process, and nuclear power covers the inefficiency of such a process.

Downsides include:

1. It's only neutral. It doesn't remove gases we've already released.

2. The process is almost certainly extremely expensive. Until something like emissions taxes are levied, it will not be a competitive fuel.

[robotresearcher]

It's slightly better than neutral. Captured atmospheric carbon would be stored out of the atmosphere in fuel tanks until use. And we could decide to capture and sequester more than we plan to burn again, since in this scenario we have the capturing tech sorted out.

[loeg]

Sure, under the assumption it's cheap to sequester more than all of the oil we extract out of the ground and consume today, then some could be stored to make it neutral or even positive. There are two big steps in there that might or might not ever happen.