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Aviation

Worldwide, air travel is increasing rapidly.

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Energy and Emissions

Commercial aviation has improved its energy efficiency over time, and recent mainstream estimates place its energy consumption at 1200-3700 kilojoules per passenger-kilometer. Short flights (under 1000 km) and intercontinental flights tend to be in the same range, per-km.

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Figures for general air travel are estimated from the Federal Aviation Administration 2, the IEA 3, and the National Cooperative Rail Research Program 4, for short flights (under 1000 km) from the Bureau of Transportation Statistics 5, Kwan 6, and Prussi and Lonza 7, and for intercontinental flights from Abdul et al. 8, the BTS 5, and Kwan 6. Energy for vertical takeoff and landing (VTOL) is estimated from Kasliwal et al. 9 and is assessed for a single passenger over a distance of 75-250 km, with lower per-km energy needs at longer distances. Energy for supersonic flight is estimated from Kharina et al. 10.

Emerging aviation technologies, such as personal electric vertical takeoff and landing (VTOL) vehicles, could increase energy demand. While there are no commercial supersonic flights available today, several companies are working to bring them back for business travelers in the 2020s. They will be significantly more energy-intenstive than comparable subsonic flights. Even more advanced forms of flight, such as hypersonic (at least five times the speed of sound) aircraft 11 and suborbital aircraft 12, are under development but far from commercialization.

Long-haul aviation requires fuel with density comparable to kerosene or greater. Barring major aircraft redesign or a technological breakthrough, methanol, ethanol, ammonia, hydrogen, and batteries are unsuitable for aviation except possibly for short distances or for small or personal aircraft 13. Low carbon alternatives to petroleum-based jet fuel include biofuels and electrofuels.

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Sources: de Jong et al. 14 and Katebi and Carlsson 15.

References

  1. The World Bank. "Air transport, passengers carried". Accessed February 3, 2023. ↩

  2. Federal Aviation Administration, Office of Environment and Energy. "Aviation Emissions, Impacts & Mitigation: A Primer". January 2015. ↩

  3. International Energy Agency. "The Future of Rail". January 2019. ↩

  4. National Cooperative Rail Research Program. "Comparison of Passenger Rail Energy Consumption with Competing Modes". Transportation Research Board, The National Academies of Science, Engineering, Medicine. Sponsored by the Federal Railroad Administration. 2015. ↩

  5. Bureau of Transportation Statistics. "Table 4-20: Energy Intensity of Passenger Modes (Btu per passenger-mile)". Accessed May 23, 2019. ↩ ↩2

  6. Kwan, I. "Planes, Trains, and Automobiles: Counting Carbon". The International Council on Clean Transportation. September 2013. ↩ ↩2

  7. Prussi, M., Lonza, L. "Passenger Aviation and High Speed Rail: A Comparison of Emissions Profiles on Selected European Routes". Journal of Advanced Transportation, Article ID 6205714, 10 pages. 2018. ↩

  8. Abdul, R., Beiting, J., Johnston, E. "Ultra Efficient Commercial Transport Challenge - NASA Design Challenge- X-JAB-ECT". Kennesaw State University, Senior Design Project for Engineers. Spring 2018. ↩

  9. Kasliwal, A., Furbush, N., Gawron, J., McBride, J., Wallington, T., De Kleine, R., Kim, H., Keoleian, G. "Role of flying cars in sustainable mobility". Nature Communications 10, Article Number 1555. 2019. ↩

  10. Kharina, A., MacDonald, T., Rutherford, D. "Environmental performance of emerging supersonic transport aircraft". The International Council on Clean Transportation, Working Paper 2018-12. July 2018. ↩

  11. Boeing. "Early Look: This aircraft concept shows a hypersonic vehicle for passengers". June 2018. ↩

  12. Sippel, M. "Promising roadmap alternatives for the SpaceLiner". Acta Astronautica 66 (11-12), pp. 1652-1658. June-July 2010. ↩

  13. Turner, J. "Low-Carbon Aviation - How can this be achieved?". University of Bath, Department of Mechanical Engineering, Powertrain & Vehicle Research Centre. Accessed December 6, 2019. ↩

  14. de Jong, S., Antonissen, K., Hoefnagels, R., Lonza, L., Wang, M., Faaij, A., Junginger, M. "Life-cycle analysis of greenhouse gas emissions from renewable jet fuel production". Biotechnology for Biofuels 10(64). March 2017. ↩

  15. Katebi, D., Carlsson, O. H. "A comparative study on the prospects of sustainable aviation fuels in Sweden". Bachelor of Science Thesis, KTH School of Industrial Engineering and Management. July 2020. ↩