According to the aviation industry, it was responsible for 7.3% of UK CO₂ emissions in 2017 (37 MtCO₂ out of a total of 503 MtCO₂*).
In 1990 UK aviation emissions were 17 MtCO₂; ie they've been rising at a rate of 2.9% per year.
There are two approaches which would allow us to continue flying without further increasing CO₂ in the atmosphere: 1) biofuels and/or 2) carbon capture and storage.
Existing planes can run on a 50:50 mix of traditional and sustainable jet fuel. A handful of airports already allow airlines to add biofuel when they refuel. For example, at Oslo Avinor airport in 2016 0.2% of total fuel loaded was biofuel.
It would be possible to design planes that run off 100% biofuel. And it would be possible for biofuel production and its shipping to be carbon-neutral.
We could halve aviation per-mile emissions in the short-term and eliminate them entirely in the long-term, if flyers were willing to pay the extra to switch to biofuels produced carbon-neutrally. This would increase the cost of flights several times over. Note: this would represent the true cost of flying. If we all had to pay the true cost, it's likely demand would fall significantly.
Warning! biofuel production uses a lot of land and agriculturally viable land is a globally limited resource.
Carbon Capture and Storage
Carbon capture and storage (CCS) is a technology that would remove CO₂ from the atmosphere and lock it away in a stable solid such as calcium carbonate, aka limestone. This technology does not exist yet! at least there's no large-scale, financially viable solution.
Microsoft and Jeff Bezos have independently announced billion-dollar programmes "to accelerate the global development of carbon reduction, capture, and removal technologies".
It might be possible to burn wood in power stations and capture most of the CO₂ released. This would significantly reduce the electricity output but would be an overall carbon-negative system, which would remove from the atmosphere the CO₂ released by our fossil-fuel-powered flights.
If we were able to invent a viable method of carbon capture and storage, it would also be urgently required to remove the CO₂ generated by other industrial processes. For example, concrete production causes 4-8% of worldwide man-made CO₂ emissions, and half of those emissions come from the chemical process, even if the process is powered by sustainable energy.
Warning! growing trees to burn in power stations uses a lot of land and land is a globally limited resource.
Bidding against other users for a finite supply of carbon capture and storage to offset CO₂ released by aviation is likely to significantly increase the cost of flying.
Many airlines offer (or allow you to pay a surcharge) to offset the CO₂ emitted by your flight by emissions-reduction measures. Typically, someone in the developing world will be given a more fuel-efficient stove or some trees will be planted.
It's hard to be absolutely certain that the stove reaches the recipient and is used correctly. It seems weird to be planting a few trees while the Amazon rainforest is being burned with such alacrity. The new tree plantations need to remain in position in perpetuity, otherwise the CO₂ absorbed will be released (sustainable harvest and replanting would be okay).
Warning! land to plant extra trees on is a globally limited resource. Warning! there are a finite number of people to benefit from emissions-reducing gifts.
Current carbon-offsetting can only mitigate aviation's CO₂ emissions in the short-term. They are all measures we should be pushing ahead (as well as reducing our flying) to try to slow the increase in atmospheric CO₂ levels.
- Decarbonisation Road-Map: A Path To Net Zero - Sustainable Aviation
- Sustainable Aviation Fuels Road-Map
- BBC World Service - Global Business - Flying Green?
* PS I think the figure of 503 MtCO₂ for 2017 UK emissions in the Sustainable Aviation report is wrong. It appears to be the number for Territorial Emissions, which flatters us by ignoring emissions from aviation! The correct figure for UK CO₂ emissions in 2017 is 784 MtCO₂e, our Consumption Emissions. See The UK's True Carbon Emissions.
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