The long road to decarbonizing the aviation sector
Under pressure to reduce its environmental footprint, air transport is committed to drastically reducing its CO2 emissions. The road will be very long towards the decarbonization of the aviation sector.
What are the commitments?
Aviation accounts for between 2 and 3% of global CO2 emissions, the main greenhouse gas, according to the International Civil Aviation Organization (ICAO), a UN agency. Although weakened by the pandemic, global air traffic is expected to reach 10 billion passengers in 2050, more than double its 2019 level. That is as many more emissions if nothing is done.
The International Air Transport Association (Iata), which federates the vast majority of airlines, as well as the aeronautical industry have committed to reducing net CO2 emissions to zero by 2050.
Forty-two countries, including those of the EU, the United Kingdom and the United States, called in the “Toulouse Declaration” in February for countries around the world to endorse this objective at the next assembly of the ICAO end of September.
However, the impact of contrails left by airplanes on global warming is not the subject of any reduction commitment at this stage. Still poorly evaluated, it seems “at least as important” as CO2 emissions, according to a study by the European Aviation Safety Agency (EASA).
Decarbonization: how to do it?
The sector relies on technological and infrastructure improvements – new materials, more frugal engines, better management of the air traffic system – to do part of the way.
The engine manufacturer CFM, a joint venture between GE and Safran, is working with its Rise project on the technologies of a future engine available in 2035, reducing fuel consumption by more than 20%.
According to the European aeronautical sector (airlines and manufacturers), all of these technological improvements will make it possible to achieve nearly half of the expected gains. Iata believes they will only help with 14% of the effort needed.
Part – corresponding to 8% of the effort according to Europeans, to 19% according to Iata – will come from a system of carbon capture and emissions trading.
These improvements take time to put in place when action is needed now, insist many NGOs who are calling for limit or reduce air travel.
What role for sustainable fuels?
Sustainable aviation fuels (SAF) represent the main means to decarbonize aviation – two-thirds of the effort according to Iata, one-third according to the European aviation sector.
They are made from biomass, used oils and even, in the future, CO2 capture and green hydrogen to make synthetic fuels.
They have the advantage that they can be used directly in today's aircraft and can reduce CO2 emissions by 80% compared to kerosene over their entire life cycle.
Airbus and Boeing are committed to flying their planes on 100% SAF by 2030, but these fuels currently account for less than 0.1% of aviation fuel consumed, and are two to four times more expensive than kerosene.
To encourage their production, the EU is working on gradual obligations to incorporate SAF into kerosene, the United States on tax credits.
Decarbonisation: what about hydrogen and electric?
Electric propulsion is currently confined to small planes and future flying taxis in urban areas. The weight of the batteries needed to store the energy makes it unsuitable for airliners.
One line of development is electric hybrid propulsion: during certain phases of flight, such as take-off, an electric motor provides additional energy to the heat engine.
In the longer term, research focuses on the fuel cell to power an electric motor by eliminating batteries: electricity would be produced on board by the chemical reaction between oxygen taken from the air and liquid hydrogen carried in tanks.
< p>This research differs from that relating to the hydrogen plane, where it would be burned directly in a heat engine.
The project led by Airbus aims to enter service by 2035 of a first plane, probably short-haul with less than 100 seats at first, according to its president Guillaume Faury.
But hydrogen is almost four times larger than kerosene, which makes impossible ble its use for long-haul routes, for which SAF will remain the only fuel.