Aviation, Climate and Jet Fuel
Current Climate Impact and Future Development of Aviation
Global aviation currently emits around 800 million tonnes of CO₂ each year, accounting for approximately 2–3% of global CO₂ emissions. When non-CO₂ effects such as contrails, nitrogen oxides, and ozone formation are also considered, aviation’s total climate impact is estimated to be two to four times greater than that of CO₂ emissions alone. Global passenger traffic has already surpassed pre-pandemic levels, with demand growing particularly rapidly in emerging economies. By 2050, passenger numbers are projected to reach 2.5 times their 2019 level, driven primarily by strong growth in the Asia-Pacific region and the Middle East. Without effective policy measures, CO₂ emissions from aviation are expected to increase accordingly.
Non-CO₂ Effects of Aviation
Non-CO₂ effects of aviation arise primarily from the formation of contrails and the emission of nitrogen oxides (NOₓ). Contrails form when hot water vapor from aircraft engines enters the cold, humid air at cruising altitude and condenses. Under suitable atmospheric conditions, these contrails can develop into cirrus clouds that reduce the amount of heat escaping from the Earth into space, thereby contributing to global warming. The formation and persistence of contrails depend strongly on flight altitude and atmospheric conditions. Nitrogen oxides produced during kerosene combustion also affect the atmosphere. While they contribute to the formation of harmful ozone near the Earth's surface, at cruising altitudes they can either accelerate or slow ozone depletion, depending on the location and altitude of the emissions. These complex atmospheric processes mean that the climate impact of NOₓ varies by region and flight level. In addition, soot particles and sulfate aerosols released during kerosene combustion contribute to non-CO₂ effects, with soot having a warming effect and sulfate aerosols exerting a cooling influence. A comprehensive assessment of aviation's climate impact must therefore take both CO₂ and non-CO₂ effects into account.
Solutions
Alternative propulsion technologies that eliminate climate-damaging emissions are still far from large-scale deployment. Battery-electric aircraft may become a viable option for short-haul flights, but current battery technology is not capable of supporting long-haul aviation. Hydrogen-powered aircraft could offer a solution for longer distances, but they require entirely new aircraft designs, and the development and certification of such aircraft will take decades - making them unlikely to deliver the decarbonization of aviation by 2045. Adjusting flight altitudes and routes can reduce contrail formation, although at the expense of higher fuel consumption. While such operational improvements should be pursued, they are expected to make only a limited contribution to reducing aviation's overall climate impact.
Reducing air travel therefore remains the single most effective measure for lowering the climate impact of aviation.
Another key solution is the use of Sustainable Aviation Fuels (SAF). These alternative fuels are produced from renewable feedstocks such as residual biomass, waste materials, or green hydrogen and are considered a crucial element in decarbonizing aviation. Depending on the production pathway, SAF can reduce lifecycle CO₂ emissions by 65% - the minimum threshold required for advanced biofuels under current legislation - to well over 90% compared with conventional fossil kerosene. SAF can also help reduce aviation's non-CO₂ effects. Their lower sulfur and aromatic content results in fewer soot particles during combustion. Because soot particles act as condensation nuclei for ice crystal formation at cruising altitudes, lower soot emissions can lead to fewer persistent contrails and cirrus clouds, thereby reducing their short-term warming effect. Synthetic aviation fuels may also slightly reduce nitrogen oxide (NOₓ) emissions, lowering ozone formation at high altitudes - a short-lived but climate-relevant greenhouse gas. Another major advantage of SAF is that their chemical composition closely resembles that of conventional jet fuel, allowing them to be used in existing
aircraft engines and airport infrastructure without technical modifications. Despite these advantages, Sustainable Aviation Fuels remain significantly more expensive than fossil kerosene. At our demonstration plant in Werlte, production costs are currently around 40 times higher than those of conventional jet fuel. Even at full industrial scale, SAF production is expected to remain four to eight times more expensive than fossil kerosene. In addition, current production capacities are still limited, restricting large-scale availability. Without clear and stable policy frameworks, many investors lack the certainty needed to finance new SAF production facilities. Governments therefore need to establish targeted support schemes, blending mandates, and market incentives to accelerate the deployment of sustainable aviation fuels.
Fortunately, the EU has already taken important steps in this direction. Under the ReFuelEU Aviation initiative, mandatory blending quotas for Sustainable Aviation Fuels (SAF) have applied since 2025. From that year onward, at least 2% of aviation fuel supplied at EU airports must come from sustainable sources. This share will increase to 6% by 2030 and 70% by 2050. In addition, a dedicated minimum quota for Power-to-Liquid (PtL) fuels will be introduced from 2030, starting at 1.2% and rising to 35% by 2050. Despite these measures, investors and potential SAF customers remain hesitant, making further political action - particularly financial support for market entry - essential. At the same time, policymakers must provide stable and reliable long-term frameworks and avoid policy reversals, such as Germany's previously adopted and subsequently abolished PtL blending mandate, which created uncertainty and delayed investment. Only through international cooperation and consistent long-term policies can SAF become a cornerstone of climate-friendly aviation.
More information on this topic can be found here:
https://www.atmosfair.de/en/air_travel_and_climate/flugverkehr_und_klima/