Identifying CO2 Reducing Aircraft Technologies and Estimating their Impact on Global Emissions

Autor: Arno Apffelstaedt



The strong growth in worldwide air traffic has raised concern on aviation’s impact on climate change. According to latest scientific estimates, carbon dioxide is one of the main contributors of aviation to global warming, accounting for up to the half of its entire positive radiative forcing. As a reaction to these findings, there is an increased interest among the industry, scientific community and governments in possible approaches to mitigating the carbon footprint of aviation. Aircraft CO2 emission is set by six technological key parameters, which define the range, the engine’s efficiency, the aircraft’s efficiency in terms of aerodynamics and weight, and the fuel efficiency in terms of heat content and fuel-specific CO2 emission. A parametric study on the single influence of the parameters is conducted, which gives engine efficiency, fuel heat content and the zero-lift drag coefficient as the most powerful technological levers. Future aircraft technologies are identified through a literature study. Some of the most promising concepts for a medium-term application are found to be laminar flow technologies, geared and open rotor engine architectures, new materials for primary structures and bio-fuels. A method is developed and applied to assess the future fleet built-up through 2036. New aircraft programs as well as phase-out of in-service aircraft are considered. Individual aircraft’s projected fuel efficiency and operational characteristics are introduced to assess the overall fleet’s CO2 emission development over the considered time frame. Three scenarios are established to simulate different future rates of technology progress and thus the possible implementation of identified technologies on future aircraft. Besides the individual aircraft‘s technological advances, further measures to reduce CO2 emissions on a fleet level are analyzed: Bio fuels, shorter aircraft program cycles and shorter aircraft life. It is shown that the sole aircraft-related technology improvements will not be sufficient to reach such goals as ‘carbon neutral growth’ due to a constantly high traffic growth rate. Bio fuels seem to be the only solution for this problem, however, this technology is still immature and thus subject of high uncertainty in terms of economic viability as well as net-carbon footprint.