Aviation is responsible for around 3% of global emissions, and will be one of the hardest sectors to tackle.
I'd rather we worry about what we can do more easily elsewhere right now--replace fossil fuel plants with nuclear, eat less beef, solar on our roofs, and such. Solid state batteries, cheaper and better than lithium, are probably the big game changer to push the masses into EVs. I don't really like the idea of biofuels, just seems a waste of land and resources--hydrogen from renewables for airlines maybe but there's bigger fish to fry in the meantime.
Good analysis. I spent a career of 34 years working to improve the efficiency of jet engines, but after 70 years of development the modern aero-engine is a highly optimised device. There is not much more to come, and that is why industry is banking on hydrogen, electric power and sustainable aviation fuel (SAF). I think the first 2 will help short and medium haul flights a lot, but long range flights will have to rely on SAF to drastically reduce their CO2 emissions. I am sceptical that SAF will be viable, so I will be very interested in Part 2!
Short to medium length plane trips can/will be replaced by electric rail.
This seems to neglect contrails, which are also an important factor.
I used to work in IT for an oil company helping provide data for profitability analysis. I wasn't an analyst myself but the impression I got was that our company lost money on jet fuel. We had to make it as part of the process to generate motor fuel where all the profits were made. I'm not sure what happens to the price of jet fuel once motor fuel sales go away.
Not really that difficult. Either it moves to zero co2 emitting fuel (say bio-kerosene) or CCS makes it cheaper to burn kerosene in jet engines and then suck it out of the air. My guess is the latter.
This is going to sound naive but how do oil companies get subsidized?
Looking fwd to Pt 2!
Thank you Hannah for this great overview! Super helpful to have the calculations for everyone on Earth taking one short or long haul flight to get a feel for how unevenly flying is distributed today.
As you write, demand reduction for today’s frequent flyers is necessary to meet climate targets. In case folks are interested, I have some practical advice on “How to fly less” from my research & experience: https://wecanfixit.substack.com/p/how-to-fly-less
Great read, thanks for sharing! I see headlines about more sustainable aviation fuels out there already - what are the main barriers to rapid adoption? Cost?
Hi, you mention how much a single person expends in CO2 during a long haul flight but not, I think, how this relates to everything else they expend CO2 doing aka what percentage is a short haul flight of an average person's CO2 use?
Nice overview, I'm looking forward to part 2. Will you discuss the potential for electrofuels (kerosene produced using captured carbon and electrolyzed hydrogen) as an alternative to biofuels? While the technology is still at an early stage and would need to be scaled massively, my understanding is that there are a lot of very serious questions around the overall impact of biofuels, land use being at the top of the list. Also it can be a bit tricky to analyze things in isolation, e.g. the biomass and/or land needed for biofuels for aviation might also be needed for other sectors.
> This gives us two levers for reducing emissions: cut demand, or rapidly scale technological innovations.
Though of course if the goal is to reduce (net) emissions all the way to zero, then we can't get to the finish line by reducing demand. Of course reducing demand can make it easier to achieve the necessary scale on zero-net-emission technologies, but it is not exactly a substitute for technological solutions.
When I buy tickets to fly around Europe I am always presented with the option to pay a bit extra for a "GREEN" something or other. What is this? and, is this actually useful and going to a good cause or is it just money in the airline's pockets?
An alternative is to use the high temperature heat of advanced nuclear reactors to create hydrogen from water via the copper-chlorine, retrieve CO2 from seawater using new pH swing cycles and refine the results into -CH2- chains of gasoline, diesel, and jet fuel. Making this work economically will require time and money on the scale of LNG production, and we should fund and begin such chemical engineering. New nuclear energy from MSRs, HTGRs, SCFRs can be delivered as high temperature (550°C) heat at 1 cent/kWh(th) and 3 cent/kWh(e). Read
https://www.realclearenergy.org/articles/2023/09/20/hot_heat_harvests_hydrogen_980866.html for an introduction and links to references.
We were wondering about ghost flights, a phenomenon we heard about a few years ago: planes flying totally empty.
Since you calculate passenger km I was wondering whether you included those emissions or not? Maybe it is not such a big part of total emissions, I don't really know. It could be negligible even though empty flights are an outrage anyway
Planes are used to transport goods as well. For example, strawberries are grown in Africa and flown to Europe. In my opinion, we could reduce an enormous amount of emission by reducing this kind of flights