1. The challenges of decarbonizing aviation
Decarbonizing aviation represents one of the major challenges of the 21st century. The aviation sector is responsible for around 2 to 3 % of global CO₂ emissions, a share that could grow significantly with the expected doubling of air traffic by 2050. Faced with this reality, industry players need to reconcile economic growth with reducing their carbon footprint. International regulations, such as the CORSIA mechanism or the European "Fit for 55" plan, impose ambitious emission reduction targets, pushing airlines and manufacturers to innovate. The transition to cleaner technologies, such as sustainable fuels or electric and hydrogen-powered aviation, is becoming an absolute priority to meet these requirements while ensuring the sustainability of air transport.
2. The different types of SAF (Sustainable Aviation Fuels)
BioSAF (Sustainable Biofuels)
BioSAFs, or sustainable biofuels, are produced from renewable resources such as vegetable oils, agricultural waste or algae. Their main advantage lies in their ability to reduce CO₂ emissions by up to 80 % compared with traditional fossil fuels, while remaining compatible with existing airport infrastructures and engines. However, their development faces major challenges, including competition with food crops and the limited availability of raw materials. These constraints raise ethical and logistical questions about their large-scale production.
e-SAF (Synthetic Fuels)
e-SAF, or synthetic fuels, are made from green hydrogen and captured CO₂, using a process called Power-to-Liquid. These fuels offer carbon-neutral potential, as their production is not dependent on fossil resources and does not compete with agricultural land. However, their adoption faces several technical and economic challenges.
Technical Challenges
e-SAFs do not naturally contain aromatics, which are essential for the proper functioning of today's engines. Aromatics play a key role in engine sealing, fuel energy density, ignition properties and even fire protection. Their absence can also affect fuel gauging systems and the solubility of water in fuel, posing risks of icing and corrosion. Total elimination of aromatics would require complete re-certification of aircraft, with potential impacts on their overall efficiency and compatibility with conventional fuels.
Future prospects
In the future, if the technical challenges associated with aromatics are overcome, e-SAFs could not only reduce CO₂ emissions, but also limit the formation of contrails, thanks to combustion that generates fewer pollutants and aerosols. Meanwhile, intermediate solutions, such as optimizing flight paths or using fuel blends, could be implemented to reduce overall climate impact. On the other hand, their production costs remain high, due to their substantial energy requirements and the need to use renewable energies to guarantee their sustainability. Their mass adoption will therefore depend on technological progress and falling green energy costs.
3. The Role of Carbon Removal (CDR)
Complementing emission reduction efforts, carbon removal (or "Carbon Dioxide Removal", CDR) is playing an increasingly recognized role in aviation's decarbonization strategy. Carbon capture and storage (CCS) technologies, as well as nature-based solutions such as reforestation or ecosystem restoration, could offset residual emissions that are hard to abate. For aviation, this means that unavoidable emissions could be balanced by CO₂ sequestration projects, enabling a carbon-neutral balance to be achieved. However, these solutions should not be used as an excuse to delay the direct reduction of emissions, but rather complement efforts to limit the sector's climate impact.
A recent review published in the UK (October 2025) introduces a conceptual framework particularly relevant to aviation: that of "geological net zero". It emphasizes that achieving national net zero requires residual fossil emissions to be offset exclusively by permanent forms of CDR, i.e. those capable of storing carbon for thousands of years, returning it durably to the geosphere. Conversely, temporary CDR solutions, which store carbon for no more than a few decades (e.g. via biomass or soils), cannot sustainably offset the climatic impact of fossil emissions, which persist in the atmosphere for very long time scales.
This principle of permanence directly informs the trade-offs required for the aviation sector. For France, it reinforces the need for a CDR strategy based on truly sustainable storage and integrated management of non-reducible emissions, in line with net-zero 2050.
4. Conclusion
SAFs, whether of biological or synthetic origin, are a promising solution for decarbonizing aviation. Their success will depend not only on technological advances, but also on public policy incentives and the availability of the necessary resources. An approach combining BioSAF, e-SAF and carbon elimination seems to be the most realistic way of achieving the climate targets set by the international community. In the long term, these innovations could profoundly transform the airline industry, reducing its environmental impact while ensuring its economic viability.
