The commitment is formal: the leaders of the commercial aviation sector – manufacturers, airlines, airports and government bodies – made a promise at COP21: the carbon footprint of commercial air transport will be reduced to zero by 2050!

A magnificent promise, symbolizing ambition and hope. But will it be kept? And how? What can we say today, more than 25 years in advance, about what will be the emissions of GHGs, the famous greenhouse gases, and other emissions of particles or water vapors that contribute to global warming? The aeronautical industry is estimated to be responsible for between 2% and 3% of the total. A fraction of what we owe to land and sea transport. But these are probably not singled out with such insistence, because they are deemed less capable of good behaviour than aviation.

Flight bashing and flight shaming don’t seem to be convincing passengers, no matter how convinced they are of the need to save the planet! The recovery from the Covid19 crisis and the literal collapse of air traffic is strong. Two years on, we’re back to 2019 levels: nearly 4.3 billion air passengers, for over 37 million flights in 2023. And 5 billion tickets in 2024… Growth continues at a rate of 4 to 5% a year, and the number of orders placed by airlines with aircraft manufacturers exceeds the 15,000 aircraft to be delivered, despite shortages of components and personnel! So, the way to vote, citizens, however climate-conscious they may be, want to move, travel, meet and discover their planet “by plane”. And they’re counting on the professionals to do their best to keep their word. Is this compatible? No one knows.

For the record, at the 2015 Paris Conference, the “zero emissions” target was set for 2050. Why this date? Doubtless to give ourselves enough time – 35 years, or at least we thought it was realistic – but also to mobilize the airline industry and administrations, while involving passengers. Alas, the two key factors in making this project a reality have been left aside as dream killers: the laws of physics, and those of economics, as Gilles Rosenberger, creator of “NéoFuel” and an expert on new aviation and its decarbonization efforts, explains. However, we mustn’t overlook the decades of effort that have gone into making unprecedented progress over the past 70 years: a series of revolutions in terms of reduced fossil fuel consumption, lower emissions of gases and particles, and reduced nuisance, all accompanied by flagrant results in terms of safety and, nonetheless, lower prices, making air travel accessible to all populations, including the most modest.

But that’s no reason to stand still. Since COP21 in 2015, everyone involved in the aviation industry has stepped up their efforts: laboratories and design offices are working at full capacity, start-ups are springing up at breakneck speed, and government departments, spurred on by political leaders, are supporting efforts. It’s a general mobilization. But is it enough? Yes and no, depending on your point of view. For the majority, yes, because with research in full swing, progress is assured. Minds are open to the most utopian, but also the most realistic, hypotheses. And no, for others, because the laws of physics or economics do not necessarily bend to human desires. Experience has shown that when it comes to progress, and therefore research, it sometimes takes time, a lot of time. The single example of batteries, which have been the subject of research for over 150 years, illustrates certain impossibilities or results that fall far short of expectations. Who remembers that the “Jamais Contente”, the first car to reach the outrageous speed of 100km/h, in 1899, was an electric car… which had no future until today! So let’s get on with it.

What are the leads? As always, there are many. You can’t focus on a single project or a single solution. You have to build on what you’ve already mastered. “Man discovers himself when he confronts an obstacle. But to reach it, he needs a tool. He needs a plane, or a plough. The farmer, in his ploughing, gradually wrings a few secrets from nature, and the truth he releases is universal. In the same way, the airplane, the tool of the airlines, brings man into contact with all the old problems”, wrote Antoine de Saint-Exupéry, in “Terre des Hommes”.

First track: “less aviation”. Reducing travel, controlling it, or even reducing the use of air transport in favor of more Eco-friendly land or sea transport can help decarbonize the planet. However, we cannot expect satisfactory results. Its effects on the economics of air transport will be catastrophic, reducing manufacturers’ R&D budgets, increasing the costs of all air transport players, and cascading down to ticket prices. This formula is unlikely to be popular or effective in the long term. But it does have its advantages.

Another possibility would be to bring about an ecological leap in “conventional” aviation, taking advantage of rapid technical advances in certain areas, such as new fuels, and gradual technological breakthroughs, with fundamentally different aircraft, or at least with engines that are fundamentally clean. This type of aviation is already being developed, or is yet to be invented.

New aircraft are constantly becoming cleaner. This is already part of the answer. More than half of today’s aircraft will be replaced in the next 10 years by cleaner ones. The other half in the following 10 years. Airlines are now required to use SAF (Sustainable Aviation Fuels), the new sustainable fuels replacing petroleum derivatives. 2% of refuelling in Europe. So small proportions, but 100% by 2035. Production and distribution must be guaranteed. Aircraft engine manufacturers have undertaken to ensure that their turbojet engines, which already accept 50% SAF, will be able to run on 100% SAF, with the issues of gums and aromatics contained in oil resolved before 2030. This leads to an 80% reduction in Co2 emissions. But the energy sources needed to produce these FAS from biomass, fatty waste and CO2 captured from the atmosphere will have to be available: green, renewable energies such as solar, wind or nuclear power.

Other avenues still require further work and experimentation: the use of green hydrogen (which still needs to be produced in large quantities) in liquid or gaseous form, consumed directly by turbojet engines, and the use of fuel cells powered by hydrogen and oxygen from the ambient air. The main issues here are storage (heavy or bulky), transport and handling (tricky), production and, ultimately, cost. Electrical hypotheses are also being evaluated. New-generation batteries, lighter per KW/h supplied, faster to recharge, offering greater autonomy, for certain aircraft models and certain categories of aircraft with small capacity, short distances and small numbers of passengers. To be defined by experience. The projects are numerous. Some are even planning to include a “thermal” source on board, a small engine using SAF, to supplement or replace the batteries to power exclusively electric motors. The Académie de l’Air et de l’Espace has published three documents available free of charge on its website*, including the latest “dossier”, number 55, on decarbonized aviation in 2050. But others have preceded: “How will we fly in 2050? Issue 38. Also opinions: “Vers un Transport aérien décarboné” Issue 20. But we can also read studies on the use of hydrogen for air travel, the use of drones in urban transport, etc.

The field is vast. The questions crucial. Opinions are still very divided. One thing is certain: the first expected results will come from the evolution of engines and the use of SAF. Then, depending on research results, there will be leaps and bounds. The pace of aircraft production and certification is measured. So we need to give it time. But it seems to me that the COP 21 target of 2025 is within reach. An optimistic view. Others, like Gilles Rosenberger, are convinced that we won’t be able to avoid a decline in air transport. If this is inevitable, won’t it lead to a far-reaching decline in the economy and in people’s quality of life? We’ve reached the frontier between politics and philosophy: and therefore science, as my friend and former chronicle companion Michel Serres would no doubt have concluded! Michel Polacco For AeroMorning

Links :

https://academieairespace.com/les-dossiers/

Review by Michel Polacco for AeroMorning.com