I hope there is further work on renewable aviation fuels, as vehicle fuels in general will be a big source of demand for fossil energy extraction for quite a while, and especially for aviation applications.
"Renewable energy in transport" report by IEA (.PDF)
That presentation leans heavily on biofuels/biomass as precursors to liquid fuels. In fact it doesn't mention any non-bio alternatives. That's not surprising given its age. Less than a decade ago biofuel looked cheaper than fully synthetic liquid electrofuels, considering the much higher cost of solar power back then.
I think that "power to liquids" is a much more likely path for large scale replacement of aviation fuel.
See for example "Power-to-Liquids as Renewable Fuel Option
for Aviation: A Review"
The main problem with biomass is land requirements. You can get a little biomass "for free" just by using scrap from existing industries, but it rapidly runs into problems of land availability if you want to make enough carbon-neutral fuel for the world's commercial airlines. There's more than an order-of-magnitude improvement in usable power density if you replace biofuel plantations with an equal area of solar farms for making electrolytic hydrogen from water, plus a synthesis/refiner complex for hydrogenating CO2 and building up liquid hydrocarbons from the resulting methanol. It's also a lot less water-intensive and doesn't require any fertilizer.
Ground transportation is a much larger component than aviation and has known solutions. If we got to 80-100% electric cars and trucks before converting one turbofan to <unknown alternative> it would still be major progress.
And in the worst case there are always biofuels or synthetic non-fossil liquid fuels, which are a lot more carbon neutral after you convert the energy that goes into their production away from fossil sources.
Right, now that ground transportation is close to being solved, we need to get creative with air travel. It's about 2% of global emissions and it's a much harder problem.
If we can cut 98% of emissions we'll be fine. 2% is not worth worrying about. While it may be a sexier engineering problem reality is ground transportation isn't close to being solved.
Gas cars still have huge momentum and infrastructure advatanges. No electric cars is being targeted for the mass low end demographic. We need the Honda civic of electrics.
Hybrid electric jet engines are being developed, and have real potential to improve fuel economy. A substantial improvement in fuel economy could mean carrying less fuel, which in turn improves fuel economy.
But if you’re talking about plug-in electric, the challenge is presumably battery weight versus fuel weight.
Yes, they'll still probably have to carry liquid fuel because nothing else has the energy density required. But maybe we can make this fuel from a carbon-neutral source instead of oil pumped out of the ground.
Research is coming along. https://arstechnica.com/science/2018/10/tonight-a-virgin-atl... It's not at the point yet where we can take CO2 out of the air, but we can probably take exhaust fumes from power plants or steel mills and make something useful out of it.
I think that "power to liquids" is a much more likely path for large scale replacement of aviation fuel.
See for example "Power-to-Liquids as Renewable Fuel Option for Aviation: A Review"
https://onlinelibrary.wiley.com/doi/pdf/10.1002/cite.2017001...
The main problem with biomass is land requirements. You can get a little biomass "for free" just by using scrap from existing industries, but it rapidly runs into problems of land availability if you want to make enough carbon-neutral fuel for the world's commercial airlines. There's more than an order-of-magnitude improvement in usable power density if you replace biofuel plantations with an equal area of solar farms for making electrolytic hydrogen from water, plus a synthesis/refiner complex for hydrogenating CO2 and building up liquid hydrocarbons from the resulting methanol. It's also a lot less water-intensive and doesn't require any fertilizer.