May 26, 2021 | DLR research study – DEPA 2050

Reduction in air transport emissions requires intensified efforts

  • Fleet-wide blending of sustainable aviation fuels at a ratio of 80 percent enables trend reversal in air transport carbon dioxide emissions.
  • Air transport needs accelerated development of alternative propulsion concepts to meet climate targets by 2050.
  • Focus: Aeronautics, air transport climate-friendly flight.

Industry, policymakers and researchers are aiming for climate neutrality in air transport by 2050. To achieve this, carbon dioxide emissions from air transport should initially be kept constant at the level which prevailed at the beginning of the 21st century, despite the expected traffic growth. In addition, further efforts are needed to continue reducing carbon dioxide emissions. A research study by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) has now concluded that only the use of Sustainable Aviation Fuels (SAFs) with a fleet-wide blending ratio of 80 percent by 2050 will make it possible to reverse the trend in air transport carbon dioxide emissions from 2035.

"This progressive scenario already takes into account continuously improving aircraft technologies and additional efficiency improvements in en-route air traffic management," explains Markus Fischer, Director of Aeronautics Research at DLR. "The emissions-related analyses of the study show that the climate targets for air transport cannot be achieved by 2050 with the current state of research. Accelerated development of alternative propulsion concepts combined with SAF blending rates of 80 percent are needed for a significant trend reversal by 2050."

"In the Development Pathways for Aviation up to 2050 (DEPA 2050) study, we analysed two particularly likely scenarios for air transport up to 2050 in an interdisciplinary team," explains Project Manager Alexandra Leipold from the DLR Institute of Air Transport and Airport Research in Cologne. "Our conservative scenario assumes continued moderate technological developments in aircraft technology and horizontal flight efficiency. Despite those efficiency improvements, climate-relevant emissions will continue to rise due to the forecasted growth in air traffic. In addition, a progressive scenario with new technologies, processes and extensive use of sustainable aviation fuels at least points the way to reversing the trend in global air transport emissions despite growth." The DLR study examined in detail the expected future emission developments in both scenarios and the resulting climate impact with regard to aircraft technologies, air traffic management and SAFs.

Given the long development cycles in aeronautics, it is unlikely that there will be a comprehensive market penetration of emission-free alternative propulsion concepts based on hydrogen by 2050. Consequently, these are not included in the study. However, if development programmes and the market introduction of climate-friendly propulsion systems, especially with hydrogen as an energy carrier, are significantly accelerated, these technologies could significantly reduce the carbon dioxide emissions of global air transport ahead of the 2050 deadline. In the future, it will be necessary to investigate more closely how the climate impact of the non-carbon-dioxide emissions of these propulsion systems will turn out, for example, through the formation of condensation trails. The requirements that will arise with regard to the necessary infrastructure, such as with the introduction of electric and hydrogen-powered aircraft will also need to be assessed in more detail.

Challenge – reducing emissions despite air traffic growth

However, reversing the trend in greenhouse gas emissions from air transport remains a particular challenge given the projected long-term growth of the industry, and the lasting effects of the COVID-19 pandemic are still difficult to assess. Before the pandemic, the researchers had expected international passenger flights to roughly double from 31 million flights in 2014 to 61 million in 2050. Additional changes in connectivity and network design are expected to result from the market entry of supersonic aircraft and unmanned aerial vehicles in the air taxi sector from around 2030. The potential growth of these new market entrants was also examined as part of the study, based on forecasts of future aircraft movements and fleet development.

Furthermore, in the DLR study DEPA 2050, scientists concluded that air transport will continue to make a significant contribution to social prosperity and general economic growth. Considering the situation before the pandemic, the number of jobs generated by air transport worldwide is expected to grow from about 19 to 39 million by 2050. Across the EU, this would increase the number of related jobs from about 2.4 million to more than 3.7 million.

DLR – research for climate-neutral air transport

The consequences of climate change demand action for climate-neutral air transport. This involves new technologies that will also ensure global mobility in the future. With its 25 institutes and facilities in the field of aeronautics research, DLR is driving this change forward with technologies for sustainable, environmentally compatible flight. Expertise from DLR's research programmes in space, energy and transport will also play an important role in this.

DLR has systems expertise in aeronautics research and sees itself in the role of an architect. DLR’s goal is 'emission-free air transport', in order to achieve the climate targets that have been set. In doing so, the results of research must flow directly into the development of new products.

There is a considerable need for research and development on the path to climate-compatible air transport, which requires continuous funding and support. Much of this needs to be researched at a fundamental level, tested in practice and approved. DLR can do this with large-scale facilities such as its research aircraft, propulsion demonstrators and large-scale computers. In 2020, DLR published the white paper 'Zero Emission Aviation' together with the German Aerospace Industries Association (Bundesverband der Deutschen Luft- und Raumfahrtindustrie; BDLI). DLR is currently working on a Zero Emission strategy

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Falk Dambowsky

Head of Media Relations, Editor
German Aerospace Center (DLR)
Corporate Communications
Linder Höhe, 51147 Cologne
Tel: +49 2203 601-3959

Alexandra Leipold

German Aerospace Center (DLR)
Institute of Air Transport and Airport Research
Air Transport Research
Linder Höhe, 51147 Cologne