# Gobbling Up Holiday Carbon

## Introduction

 Fig. 1: Norman Rockwell's "Freedom From Want" (1943, oil on canvas). (Source: Wikimedia Commons)

Anyone who's passed through airport security in late November can tell you that Thanksgiving is the busiest travel time of the year. According to the Transportation Security Administration, about 2.3 million people were screened at US airports on the day before Thanksgiving 2021. [1] It's no secret that flying has a significant impact on global climate change. [2] So as you slice your second helping of pie to soothe yourself from the bickering relatives sat on either side of you, you may be asking yourself whether that carbon emission was worth it, or at least if there is something that you could do to decrease your total Thanksgiving carbon footprint. Unfortunately, the turkey that you've just eaten adds insult to injury, as meat is the dominant source of greenhouse gas emission from food production. [3] Perhaps it's possible to offset the carbon added to the atmosphere by your Thanksgiving air travel by removing a few turkeys from the dinner table?

## Calculation

Let's consider one of the biggest culprits of air travel: cross-country flights. 2,700 miles separate San Francisco International Airport and Boston's Logan International Airport, so a round-trip ticket covers 5,400 miles or 8,700 kilometers. One study has found that each mile of air travel is estimated to release, on average, 0.64 pounds of CO2 per passenger, or 0.18 kg per km travelled per passenger. [4] So, this roundtrip flight will produce about 1600 kg of carbon per passenger. Could this amount of carbon be reduced from another part of the holiday?

Let's now consider the centerpiece of the Thanksgiving dinner table, shown in Fig. 1: the turkey. One study found that a kilogram of turkey meat produces about 6.04 kg of CO2. [5] Using this finding, we would like to compute how many turkeys we should avoid raising in order to offset the extra carbon added to the atmosphere by the cross-country flight. Assuming that an average Thanksgiving turkey has about 5 kg of meat, that's 53 turkeys which must be removed to offset the flight! Of course, the turkey cannot simply be removed from the dinner table without leaving hungry guests; it must be replaced with another food. Perhaps butternut squash, another fall favorite, could be a viable substitute? At just 0.42 kg of CO2 emitted per kg of squash, it would reduce CO2 emissions by 5.62 kg per kg of food replaced. [5] To offset the roundtrip cross-country flight, that's just 280 kg of food! Perhaps a hungry guest will eat 200 g of turkey; then we would only need 1400 individuals with similar appetites to shift their diet in order to offset the roundtrip flight.

## Conclusion

Aviation is a major culprit of global climate change, and the increased demand around Thanksgiving greatly exacerbates this. To make matters worse, Thanksgiving travelers are typically on their way to a meal which itself requires a large amount of CO2 to be released into the atmosphere. In order to offset the carbon released by one roundtrip cross-country flight, about 1400 hungry Thanksgiving diners would have to substitute their helpings of turkey for helpings of butternut squash. Unfortunately, convincing this many travelers to shift their diet may prove to be more difficult than convincing your extended family of your political views while seated around the table.

© Toby Satterthwaite. 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] H. Murphy, "Thanksgiving Air Travel Rebounds, Nearly Hitting 2019 Levels," New York Times, 25 Nov 21.

[2] E. Rosenthal, "Your Biggest Carbon Sin May Be Air Travel," New York Times, 26 Jan 13.

[3] O. Milman, "Meat Accounts For Nearly 60% of All Greenhouse Gases From Food production, Study Finds," The Guardian, 13 Sep 21.

[4] J. P. Padgett et al., "A Comparison of Carbon Calculators" Environ. Impact Assess. Rev. 28, 106 (2008).

[5] S. Clune, E.Crossin, and K. Verghese, "Systematic Review of Greenhouse Gas Emissions For Different Fresh Food Categories," J. Clean. Prod. 140, 766 (2017).