Estimating Private Aviation Emissions

Introduction

Fig. 1: Growth of private aviation. [2] (Source: T.Ahmad)

Global aviation is major contributor to CO₂ emissions, contributing 2.4% in 2018 to athroprogenic CO₂ emissions. [1] While this topic receives significant attention, the subtopic of private aviation (sometimes used interchangeably with business aviation) is less studied or acknowledged in terms of CO₂ emissions impact. This might be because the data on private aviation is more disparate. This report estimates the CO₂ emissions of the US and global private aviation sector in 2021. There are two reasons why this topic is particularly important: firstly, private aviation moves around a small fraction of people who can afford the high prices, and hence contributes more per capita emissions than average fliers; secondly, this form of travel has become considerably more popular post-Covid, likely due to health and safety concerns (Fig. 1). [2]

Analysis

The first approach is to estimate this impact for the US market and then apply a market share % to scale it at the global level. According to the Federal Aviation Administration (FAA), there were 5,099,012 business jet flights that occurred in 2021, including both domestic and international travel. [3] For the average flight time, I use the FAAs FY2021 reported statistics of 2.25 × 10⁷ hours of annual flight time and 1.30 × 10⁶ flights handled to estimate an average flight time of 1.7 hours. [4] The average jet fuel consumption per hour is 1,400 kg. [5]

Multiplying these three figures together gives a total fuel consumption of 12.1 billion kg. To get the CO₂ emissions, we can simply multiply the fuel consumption by 44/14 (molar mass ratio of CO₂ to oil) - this gives us 38.1 billion kg of CO₂. The US has 69% of the global market share for private aviation; using this leads to an estimated global CO₂ emission of ~55 billion kg.

The second approach to triangulate the estimate is to use prior estimations of private aviation emissions as a fraction of total aviation emissions. The IEA estimated 2021 emissions at 720 Mt (or 720 billion kg). Assuming a 4% share of private aviation, this results in ~29 billion kg of CO₂ emissions globally. This is half the magnitude of the estimate above, likely due to data disrepancies and definitional issues about which flights are counted. [6]

It is important to note that CO₂ is not the only greenhouse gas emitted and that water vapor, NO_x, etc. also contribute to global warming. The total estimated global warming potential of all emitted substances is ~2-5x of CO₂, so the CO₂e emissions for private aviation range between 49-122 billion kg. [7]

Conclusion

The private aviation industry has been receiving more attention recently. This report provides an estimate of the emissions impact and puts into context the relative importance of this sector from a global warming perspective.

© Taimur Ahmad. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

References

[1] D. S. Lee et al., "The Contribution of Global Aviation to Anthropogenic Climate Forcing for 2000 to 2018," Atmos. Environ. 244, 117834 (2021).

[2] J. B. Sobieralski and S. Mumbower, "Jet-Setting During COVID-19: Environmental Implications of the Pandemic Induced Private Aviation Boom," Transp. Res. Interdiscip. Perspect. 13, 100575 (2022).

[3] "FAA Business Jet Report," U.S. Federal Aviation Administration, January 2022.

[4] "Air Traffic By The Numbers," U.S. Federal Aviation Administration, May 2022.

[5] S. Gössling, "Celebrities, Air Travel, and Social Norms," Ann. Tour. Res. 79, 102775 (2019).

[6] S. Gössling and A. Humpe, "The Global Scale, Distribution and Growth of Aviation: Implications For Climate Change," Glob. Environ. Change 65, 102194 (2020).

[7] "The Growth in Greenhouse Gas Emissions from Commercial Aviation," Environmentaland Energy Study Institute, June 2022.