Monday, September 25, the President of the Republic unveiled ways to achieve carbon neutrality in 2050. The result of work carried out for more than a year by the General Secretariat for Ecological Planning (SGPE), this plan aims to reduce French greenhouse gas (GHG) emissions by 33.8% in 2030 compared to 2022.

But in his “French-style ecology” project, Emmanuel Macron does not envisage any constraints or major ruptures, as the subject of gas boilers illustrates: the president assumes to “encourage” the French “without prohibition, but encouraging them to change more quickly.” But this choice could well prove unsuitable for decarbonizing land and air transport.

The aviation sector is emblematic of the difficulties posed by a legally non-binding ecological transition. Greenhouse gas emissions from French civil aviation have only increased since the appearance of this sector, with the notable exception of the last three years, affected by the Covid-19 pandemic. However, the government plan envisages a reduction of 12 million tonnes of CO2 by 2030 compared to 2019, i.e. a halving of the sector’s emissions in seven years.

Decarbonization levers exist, but those that current planning intends to activate have either late or very limited effects.

The document published by the SGPE recommends gradually increasing the share of sustainable aviation fuels (CAD) used by aircraft, by developing a real French sector for the production of these fuels.

Second generation CAD, derived from biomass (recycling or valorization of oils, fats, waste or agricultural and forestry residues) are distinguished from the first generation (palm oil, sugar cane) by the fact that they do not encourage deforestation and do not compete with agriculture for food. Currently, they are not produced in sufficient quantities and only account for 1% of the fuels used by global aviation.

The government intends to create a strong French sector to produce more. But that will take time. “When we put, on the one hand, the biomass resources we have available and, on the other, the needs, we can clearly see that there is a very significant imbalance. For air travel alone, with its growth prospects, it would be completely impossible to replace all kerosene with biofuels, analyzes Pierre Leflaive, responsible for transport issues at the Climate Action Network (RAC). Even if, technically, we can replace 100% of kerosene with biofuels by 2035, this can only concern a residual fleet. » In addition, “there will be competition in use with heating, building, construction, which will constrain this energy resource”.

If we could produce enough CAD to keep all the planes flying, their CO2 emissions would fall. But the latter only represent a third of the sector’s influence on the climate (what is called radiative forcing). The condensation trails that form behind planes as well as the release of ozone or nitrogen oxide into the troposphere contribute greatly to the warming effect of aviation.

The plan presented by Emmanuel Macron also recommends improving the energy efficiency of aircraft by renewing fleets with more fuel-efficient aircraft (hybrid, electric or hydrogen), thus hoping to save 3 million tonnes of carbon dioxide in seven years.

Unfortunately, the room for maneuver is limited and their effect would only be delayed: current planes are much more economical than those of twenty years ago, but the rate of improvement in their energy efficiency slows down over time (that -this was moreover largely offset by the growth in the number of flights). We would therefore have to count on an uncertain technological breakthrough to drastically reduce emissions.

And even if this happens, it cannot produce rapid effects, because the renewal of a fleet takes time: on average, an airliner remains in service between twenty and twenty-five years, i.e. a complete renewal of the park rather by 2050. We are far from a visible effect before the year 2030.

As for technologies such as hydrogen, they are very far from being mature, and their feasibility (both in terms of safety and profitability) divides professionals in the sector.

To reduce emissions from the aviation sector, “demand control”, that is to say reducing the number of flights, is the most effective lever of action, and its effects are immediate. Greater use of alternative fuels, which are three to four times more expensive than kerosene, could increase the cost of tickets for customers, and therefore reduce demand. But the incorporation of these alternative fuels will take years.

On the other hand, a tax on plane tickets or kerosene could accelerate this dissuasive effect linked to price, but the government excludes such measures, believing that they would penalize French competitiveness in a very competitive market, where the tax exemption of kerosene is global.

Ultimately, the authorities will have to rely on sobriety measures if they want to effectively decarbonize this sector. “Ultimately, there will not be a green plane, it’s a myth,” warns Pierre Leflaive. There could be, on a residual fleet, alternative fuels which will reduce gas emissions from the aviation sector. But this is only possible with a reduction in the fleet. There really is a scientific consensus on this question. »

Over the past three decades, greenhouse gas emissions linked to transport have continued to increase. In France, private vehicles alone represent almost two thirds of the sector’s emissions.

To decarbonize road transport, the plan of which Emmanuel Macron presented the broad outlines plans to act on two fronts:

– by favoring “light and economical” private vehicles to “replace the most polluting thermal vehicles” for a saving of 3 million tonnes of CO2 equivalent (Mt eqCO2);

– by encouraging the population to turn more towards electric vehicles, “with a target of 15% 100% electric vehicles driving in 2030, compared to only 1% today”, which would reduce emissions by 11 Mt CO2 eq. The government is banking on strengthening conversion assistance, the deployment of charging stations, the review of tax advantages linked to company fleets and company vehicles or the tightening of penalties to encourage the purchase and production of more fuel-efficient vehicles.

The objectives are going in the right direction, but will not be enough to change the situation, denounces the RAC. “The idea of ​​electrification of vehicles is well put forward, but not the issue of reducing the vehicle fleet and the question of the type of electrification,” laments Pierre Leflaive.

First of all, the current trend in the automobile market is far from the sobriety that the president calls for. SUVs, larger, heavier and more polluting than the average vehicle, are the most sold in Europe. In France, they represented 46% of new car registrations over the first five months of 2023, surpassing sedans for the first time.

In the same vein, if the replacement of thermal vehicles with electric cars is going in the right direction, weight remains a major issue, whatever the engine. “The benefit of electrification is reduced, because the vehicles we sell are heavy vehicles,” estimates Mr. Leflaive, and their impact in terms of production and use (life cycle) is more harmful than conventional vehicles. lighter vehicles.

The government’s objectives clash with the reality of the offer from manufacturers who favor the production of SUVs, even for the electric range. In July, the boss of Stellantis, Carlos Tavares, estimated that it was impossible to profitably produce small electric cars in France. The Minister of the Economy, Bruno Le Maire, then appealed to his “economic patriotism”, affirming that “the industrial challenge for France is to build not only high-end vehicles, but also small electric vehicles like the [Peugeot] e-208 on our territory”. A request that remained a dead letter.

To encourage sobriety, a tax on vehicle weight (penalty) has penalized, since 2021, cars weighing more than 1,800 kg (a threshold lowered to 1,600 kg in the finance bill for 2024). It only affects 2% to 3% of vehicles today and only 5% to 6% with a threshold of 1,600 kg, but could affect 40% of vehicles if the threshold was lowered to 1,300 kg. It remains to be seen whether Emmanuel Macron, who described this policy as “ecology that creates economic value”, will dare to go further than the automobile penalty.