The Greenhouse Gas Pollution of Air Travel

The question of greenhouse gas emissions from air travel is gaining more angst. I will present here a virtual trip with an estimate of its pollution from a European web calculator.

There are many aspects to this question, and I will present my hopeful solution. Air travel only contributes 2% of greenhouse gas emissions, but it is growing rapidly. There is promise of smaller, slower electric planes for trips of a few hours length. Electricity is much cheaper fuel than aviation fuel. However, 80% of the emissions are from much longer flights. The Boeing 737 Max was designed with more forward engines to save 10% on fuel. But this caused some instability that had to be corrected with a program, which could go out of control.

Before the math, I will explain that I hope that modern communications can eliminate much business and conference travel. I also hope that YouTube and 4K TVs can show you drone pictures of world sites that you can’t even see yourself, educational museum guides, and guided tours without traffic or rushing to keep up with the guides. This also allows you to avoid cramped airline seats, sick or wide fellow passengers, predators on metros, long lines, overcrowded streets, people in front of the paintings, questionable food, highly overpriced and cramped European hotels, endless reservations, etc.

Government funding for conferences has been declining, and therefore limited to more senior or leading researchers, whereas modern communications can allow all students to observe them at almost no cost. Important government agency presentations should not be limited to those who can make it to Washington D.C., which also favors nearby Eastern states.

The website that I am using is ecopassenger.hafas.de, which is available in English as well as other languages. In order to get a long range trip, I chose Rome to London. I also took the option of including greenhouse gas secondary effects as well as direct emissions. One kilogram is equal to 2.205 pounds. One liter is equal to 0.264 liquid gallons. I will leave the emissions in kilograms (kg) for ratios, but convert airline results into pounds in the end. The calculator also compares airline emissions to autos and trains.

CO2 emissions are 273 kg for a plane, 395 kg (871 lbs) for an average gasoline powered car with one passenger (less if European diesel), and 56 kg (123 lbs) by rail. However, when secondary emission effects at high altitude are added, the car and rail stays the same, but the flight is increased to 410 kg (904 lbs). The increase of 410 kg over 273 kg is a 50% increase in effective emissions. That makes the flight to auto ratio 1.04, and the flight to rail ratio 7.32. However, London to Rome is 1,780 km (1,106 miles) by car (18 hours and 43 minutes), 1,968 km (1,223 miles) by rail (14 hours and 30 minutes), and 1,440 km by air (895 miles). The flight time is only 2 hours and 30 minutes long, but extra time is added going from a city point to another city point, plus showing up early, plus baggage pickup. So they list it as 7.17 hours. A two passenger car of course gives only half the emissions per passenger, and a four passenger car gives a quarter of the emissions per passenger.

Normally, I evaluate car travel for an average 25 miles per gallon, and 20 lbs of CO2 emissions per gallon. So the round trip gives 2×871=1,742 lbs of emissions. The round trip distance is 2×1,106 = 2,200 miles. Dividing by 25 mpg gives 88 gallons. Multiplying by 20 lbs of emissions per gallon gives 1,760 lbs of CO2, agreeing with their 1,742 calculation.

US per capita CO2 emissions is 16.49 metric tons or 18.2 US tons. The round trip flight from Rome to London is then 2 x 904 lbs/(18.2 tons x 2000 lbs/ton) = 0.050, or 5.0% of US per capita emissions.

The sustainable amount of emissions in our future is 2,000 kg (4,409 lbs or 2.2 tons) per person, so the round trip flight is 820 kg/2,000 kg = 41% of the eventual greenhouse gas limit. Besides, eventually trains and cars will be electrified, and the eventual electric energy sources close to zero emissions.

The air distance from Los Angeles to New York is 2,451 miles or 3,944 km. For such a round trip flight or 4,902 miles we estimate as proportional to the 1,790 round trip flight above, giving (4,902/1,790) x 1,808 lbs = 4,951 lbs or 2.48 tons of emissions. Dividing by 18.2 tons per capita, gives 13.6% of the US per capita emissions. In 2017, California’s per capita emissions was only 10.2 tons, so the LA-NY RT flight of 2.48 tons is 24.3% of a Californian’s per capita emissions . Quite different from the 2% of worldwide emissions due to air travel.

This analysis also gives travelers and companies an estimate of how much carbon offsets are needed for various air travel.