[shawnb576]

I think the hydrogen-electric [1] development is more promising here because it has the potential to deliver long haul flights with no emissions or contrails.

While H2 isn't great for decarbonization at scale, in specific industries like aviation it might be applicable assuming it's made cleanly.

[1] https://www.zeroavia.com/

[Teknoman117]

What's the justification to expect that 25-50% of human climate impact will be from aviation by 2050?

Growing population? Lower cost of access to flight? Other industries decarbonizing and causing aviation impact to just be a larger fraction of overall impact?

[jabl]

IIRC it's a combination of air travel continuing to expand at the roughly 2.5% yearly rate it has been doing for the past decades, and other sectors of the economy successfully decarbonizing.

[kwhitefoot]

Isn't a contrail a condensation trail? In a hydrogen fuel cell the waste product is H2O so surely there is a contrail.

[cesaref]

I believe contrail formation requires nucleation sites, which is normally provided by soot particles from the burning fuel.

[someweirdperson]

Even more, because all the energy is from "burning" H2 only, no Cs to burn. Whether or not visible contrails form is a separate question. Even transparent water is highly efective outside of the visible range.

[ZeroGravitas]

If you burn the hydrogen in a turbine, you need to worry about this. If you use a fuel cell you can easily capture the water.

[zppln]

Having listened to both Boeing and Airbus recently, neither seem to see any alternatives to SAF for long haul though.

Hydrogen has it's challenges. I heard someone did the math on running Heathrow exclusively on it who came to the conclusion that you'd basically need 3-4 reactors to produce it.

[yobbo]

Hydrogen production, though, is one of the workable applications of wind turbines.