“Technology is not enough in the face of the climate emergency”

Last July, the Dutch government decided to cut 12% of flights from Amsterdam airport to reduce its environmental impact and fight noise pollution. This is the first time in Europe that such a decision has been taken in air traffic. A few days ago, the CEO of Aéroports de Paris, Augustin de Romanet, invited “people to be more reasonable in air travel” as long as “air transport will not have been at the end of its decarbonization process” even if he nevertheless specifies that, “in the long term, air transport will be the system that emits the least CO2”.

“These two examples show that this question of masterair traffic crisis is on the table », estimated Florian Simatos, teacher-researcher at Isae-Supaero, on the occasion of the innovation meetings organized on September 22 at the premises of Enac (national school of civil aviation). Florian Simatos is one of the five researchers from the prestigious Toulouse engineering school to have published in October 2021 a reference aviation and climate »a summary document of the latest scientific publications on this topic.

The authors come to the conclusion that to respect the Paris agreements and limit global warming to 1.5°C a decrease in traffic is necessary whatever the assumptionsits technologies”. CO2 emissions must decrease now and very significantly. That can shock. But what you have to understand is that there are ten years of carbon emissions left at the current rate to meet the carbon budget of 1.5°C.”, points Florian Simatos. Assuming that aviation would use 2.6 % of global carbon budgetthat notewould stop the emissions decrease by about 10 % per year. On the other hand, according to researchers with a more lax objective of keeping global warming at 2°C, a target more commonly taken up by industrialists in the sector, growth in air traffic would be possible on the condition of hypotheits technological tres ambitious according to an optimistic scenario and but a more pessimistic scenario concludes that a drop in traffic would still be necessary.

The hydrogen plane, a long-term answer

“By 2050, technology alone is not enough to lower emissions at the average rate required. Many disruptive technologies are discussed. But hydrogen aviation is not a response to the climate emergency, even if it makes it possible to envisage low-carbon aviation on a more distant horizon”believes Florian Simatos.

Before developing:

For the moment, only one manufacturer (Airbus, editor’s note) communicatede on the subject and targets a segment of the fleet, a priori, short-haul. Next, this plane needs to deploy in the fleet. And then, if during the flight the hydrogen does not generate CO2 emissions, significant emissions can take place during the production of the hydrogen. Today, if we had the choice between a thermal plane and a hydrogen device, it would be necessary to favor the thermal plane because the current methods of production of hydrogen (via natural gas) are extremely CO2 emitters. compared to fossil fuels.

It is also necessary to develop a very important sector of hydrogen production which is low carbon and we are not there yet. The set of conditions means that we estimate that hydrogen aviation would only reduce aviation CO2 emissions by a maximum of 10% by 2050. »

“The hydrogen plane will take time”, says the boss of Airbus

This observation, he is not the only one to share it. Philippe Novelli is director of the propulsion program aeronautics and environment at Onera and former head of alternative fuels at the Environment Directorate of ICAO (the International Civil Aviation Organization).

Dechar that means using sources ofeenergy that do not increase the gas content at greenhouse effect of the atmosphereeD. Gold, on can tres good to have a complete vectorement decarbone, typically the hydrogedon’t whose burning don’teabsolutely no CO2. But over the full life cycle, the hydrogenot represents up to three times the emissions of kerosene. Today 85 % of hydrogeis not produced at from natural gas. Hydrogen planes will be zero emission only if usingeelectricitye ecarbonee. »

Not to mention that the arrival of hydrogen aviation will require major upheavals in terms of aereports to store, liquefy hydrogedon’t liquid and then to refuel planes.

ADP, Airbus, Air Liquide in battle order to welcome the hydrogen plane in airports

The question of the availability of biofuels

In the shorter term, many hopes lie in the development of biofuels.

Over the entire life cycle, biofuels generate lower emissions than kerosene. Lrepr biofuelsefeel a potentially applicable pathway immequickly since planes can already fly with 50% of biofuels mixed with kerosene. On the other hand, production and consumption remain extremely low today. In particular, because the costs are high »decrypts Philippe Novelli.

The researcher also notes the importance of “make the right choice of biofuel” because not all are equal. A biofuel made from palm oil and which also contributes to the deforestation of a territory, will generate very high carbon emissions. During the last demonstration flights with 100% SAF (sustainable aviation fuel), manufacturers used used cooking oils, a solution with a very good carbon footprint. But not sure that this option can be generalized on a large scale. “If we collected all the used oils in the world, that would not even fill 5% of energy consumption.tick required for air traffic »believes Florian Simatos.

Airbus’ strategy to switch to 100% sustainable fuel flights

More generally, he notes, there is a scientific and industrial consensus that the availability of biofuels will be very limited. It will not be possible to fully decarbonize the fleet with biofuels”. All the more so, emphasizes for his part Philippe Novelli, that will be born competitionsrecommendations for the use of biomass and biofuels” : Other sectors, such as chemicals for example, will also want toto decarbonise and therefore will also require biomass. »

On the other hand, biofuels represent an interesting alternative to reduce the non-CO2 effects of aviation. “Their chemical composition is a bit different from fossil fuels. They have fewer aromatics and with an incorporation rate of 50% this can reduce radiative forcing by around 10 to 25%”raises Florian Simatos.

Last alternative considered to decarbonize aviation, electrofuels or synthetic fuels, produced fromwater, CO2 andeelectricitye. Beyond reduced CO2 emissions, these fuels could also reduce non-CO2 effects such as contrails by generating less soot. Electrofuels have a chemical composition closer to that of kerosene and therefore represent a limited impact at aircraft level (unlike hydrogen) but this technology is still in its infancy”, observes Philippe Novelli. For example, the Norsk e-fuel project in Norway plans to produce ten million liters of fuel in 2023. A drop in the bucket when you consider that the consumption of kepinkenot ewas 286 million tonnes in 2018. ” Lhe combination of different solutions is certainly necessary to decarbonize aviation. All alternative solutions are costly in terms of resources and also financially and therefore energy efficiency remains more than ever a major issue”summarizes Philippe Novelli.

Beyond decarbonization, air transport could be faced with other changes to its environment in the face of global warming. In some cities around the world, planes are already taking off at night due to very high temperatures. This is the case in Phoenix in the United States »highlights Laurent Terray, researcher at Cerfacs in Toulouse.

Toulouse scientists have been working for several years in collaboration with Airbus to measure the impact of climate change on aviation. They were able to demonstrate that the multiplication of episodes of high heat could drastically increase the number of days when planes will have to board fewer passengers to take off.

Why high temperatures will disrupt air transport

Climate change could also increase the risk of turbulence. Not to mention the risk of submersion of airports located by the sea. The rise in sea level will continue, it is an irreversible phenomenon which could worsen in the event of acceleration of global warming., adds Laurent Terray. The risk of submersion primarily concerns Southeast Asia and destinations in the Pacific. In France, Nice airport is also considered at risk and the DGAC has already started work to study the phenomenon.