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The energy transition in the transport sector is undoubtedly one of the most complex challenges of the century. How far have we got in France? Can we hope to achieve carbon neutrality in transport by 2050? Will our salvation come from technology, and is a “green airplane” really possible? These are just some of the questions that Aurélien Bigo answered in a candid interview with Tolt for our podcast “Je t’offre un rail ?”, in partnership with SNCF Connect.
An independent researcher committed to studying the energy transition of transport, Aurélien Bigo's thesis (defended at the Institut Polytechnique in 2020) looked at how we could achieve our climate objectives in the transport sector, and particularly in France. After a stint at ADEME, where he contributed to the creation of the Transition 2050 prospective scenarios, he is now devoting himself to the transitions in our mobility through his two complementary approaches: research and popularization.
In this article, we summarize the key ideas developed in the episode (but we strongly recommend you listen to it in its entirety). Dive into one of the greatest challenges of our time: the impact of our mobility on the climate!
Today, transport (passenger and freight) accounts for between 30% and 33% of GHG emissions in France. On the podium in first and second place: the car and the plane.
Cars, which account for two-thirds of all journeys in France, are the main contributors to these emissions. To better understand the current situation, Aurélien Bigo takes a look in the rear-view mirror:
“In just one century, we've gone from walking to the car as our main means of transport! This has consequences in terms of transport time, number of journeys and kilometers covered.”
Today, walking accounts for only a quarter of our journeys, ahead of public transport - including the train - which represents only 10 to 15% of trips, and cycling, which accounts for only 3 to 4%.
Over the course of a century, the French have maintained an average of one hour's transport per day, but the drastic increase in transport speed (x 10 to 12) now enables them to cover an average of 50 kilometers per day, compared with 4 to 5 kilometers previously. In short, we spend as much time moving around every day as we did 100 years ago, except that we go faster and therefore further. "Before, you could change town in 3 or 4 hours. Now, we can change regions (by car) or even continents (by plane)."
Just behind the car, the airplane ranks second in terms of kilometers traveled and greenhouse gas emissions in France (around one-third for freight transport and two-thirds for passenger transport).
Air transport accounts for 7% of CO2 emissions in France. And internationally, it is the only sector that has not begun to reduce its emissions.
Source : CITEPA Secten 2019 / Aurélien Bigo
And despite a slowdown during the health crisis, its use continues to grow.
As Aurélien Bigo points out, “airplanes encourage excessive mileage". Although comparable to the car in terms of emissions per kilometer, it allows us to cover much more distance in a shorter time, drastically increasing overall emissions per trip.
In this Carbone4's article, we can see the differences in “Carbon Intensity” according to the type of transport for a 400-1000 km trip, in the short term (without construction) and long term (with construction) :
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gCO2e/passager.km - Source : Carbone4.com - “Les idées reçues sur l'aviation et le climat”
The air transport sector is generally credited with 2% of global CO2 emissions. But this figure doubles when non-CO2 effects such as contrails and nitrogen oxide emissions are included! These impacts, though ephemeral, accumulate as air traffic grows, amplifying the impact on the climate.
While the airline industry claims to be aiming for carbon neutrality by 2050, Aurélien Bigo has a number of reservations.
The idea that technological innovations will be enough to achieve carbon neutrality is encouraging. But it is also increasingly contested.
Among the most popular are sustainable aviation fuels (SAF). Yet, according to the researcher, they have obvious limitations:
Biofuels: although they can reduce emissions, their production requires limited resources. And in particular biomass (all materials that come from plants: wood, vegetable oils such as rapeseed oil in biodiesel...), the use of which often competes with food uses and biodiversity!
Plantation de Colza (l’huile de colza étant très utilisée pour le biodiesel européen)
Synthetic fuels: they require large quantities of hydrogen and CO2, produced using low-carbon electricity. Yet the demand for electricity would be massive: achieving carbon neutrality with these fuels would require the equivalent of half the current electricity production of a country like Germany or France!
“For cars or road transport, for example, these synthetic fuels are not favored because it takes 4 to 5 times as much electricity to run a car on synthetic fuels as it does directly for a battery-powered electric car. So if these synthetic fuels are being considered by the airline industry at the moment, it's only because there aren't really any other alternatives available to decarbonize long-haul transport”.
As for hydrogen and electric power, these solutions are limited to short-haul routes, and remain uncertain for medium- and long-haul operations. They also raise questions of sustainability: “There are several sectors that are going to have to become more electrified in this transition. So reserving such massive, significant shares of electricity production for air transport is very questionable.” And as far as hydrogen is concerned, we recommend this article for a better understanding of the issues involved.
And to go further, don't hesitate to read our article on the preconceived ideas surrounding the decarbonization of the aviation sector.
For the researcher, there's no doubt about it. As Tolt sums it up: “Believing in green aircraft today is absolutely living in a rainbow.”
“The airline industry has gone from climate-skeptic to climato-rassurist to techno-solutionist. But we realize that today's techno-solutionism won't work.”
“From now on, right up to the level of the General Secretariat for Ecological Planning (SGPE) - which reports to the Prime Minister - air transport assumptions are increasingly being revised downwards. The scenarios don't add up: we have too much demand for biomass and electricity compared to the production we can reasonably envisage, and we won't be able to achieve carbon neutrality in this way by 2050.”
To find out more, we recommend this interview with Aurélien Bigo in Polytechnique Insights.
Faced with the inadequacy of technological solutions and energy constraints, planning for sobriety seems essential. Finally, as the Climate Action Network points out, the question is no longer “Should we reduce air traffic?” but “How can we reduce air traffic fairly and efficiently?
Aurélien Bigo proposes an essential concept here: sobriety by kilometer, which consists in limiting the distances travelled rather than simply decarbonizing means of transport. While aviation encourages the over-consumption of kilometers, abandoning air travel for more local routes can drastically reduce emissions.
This vision is in line with that of Jean-Marc Jancovici (also featured on the podcast), who invites us to rethink the idea of a change of scenery and travel, in order to move towards a chosen (and not submissive) sobriety.
In France, rail already accounts for 10-15% of journeys, but its potential remains under-exploited. Aurélien Bigo also encourages “intermodality” (“personally, I combine train and bike”) to meet the needs of daily or long-distance travel without resorting to the car or plane.
As Aurélien Bigo reminds us, this transition will require a systemic and collective approach, combining innovation, behavioral change and ambitious political reforms. And on the behavioral side, since reducing air and road traffic seems unavoidable if we are to achieve our climate objectives, the train appears to be the alternative of choice!
And through their testimonials, the guests of "Je t'offre un rail?" show us that train travel is not just a sustainable alternative. It's also an adventure in its own right, inviting us to rethink the way we travel!
To make sure you don't miss a single episode, and to get all the inspiration you need from our guests, don't hesitate to subscribe to the suscribe to the podcast on your favorite listening platforms. Thanks to our partner SNCF Connect, the benchmark application for trains and sustainable mobility, which accompanies more than 15 million users on their journeys in France and Europe.
Issue du monde de la communication et des médias, Sophie est Responsable éditoriale chez HOURRAIL ! depuis août 2024. Elle est notamment derrière le contenu éditorial du site ainsi que La Locomissive (de l'inspiration voyage bas carbone et des bons plans, un jeudi sur deux, gratuitement dans ta boîte mail !).
Convaincue que les changements d’habitude passent par la transformation de nos imaginaires, elle s’attache à montrer qu’il est possible de voyager autrement, de manière plus consciente, plus lente et plus joyeuse. Son objectif : rendre le slow travel accessible à toutes et tous, à travers des astuces, des décryptages et surtout, de nouveaux récits.
