By Mark Jones
I’m sure detailed questions about fuel consumption from a passenger aren’t common, but the pilots on flights 2030 and 1114 humored me. My ticket showed the emissions allotted to my seat, something I noticed for the first time. The numbers were lower than I anticipated, so I wanted to check the math. Once I had the exact amount of fuel the A319 burned from Michigan to Denver and back, some simple math would provide the direct CO2 emissions.
According to the ticket, 174 kg of CO2 equivalent emissions was my allotment for the Michigan to Denver trip — and for the trip back — only 154 kg. Air travel is a carbon-inefficient way to travel, or at least that is what I thought. As the figures seemed small, I figured the airlines were greenwashing to make air travel more palatable. It’s easy to be suspicious of airline math. There are 22 actual rows of seats on the A319, yet the last row is numbered row 35. An inability to consecutively number rows is the culprit. It is hard to be confident in more complex math when the airline can’t count.
I believed air travel would be much worse than driving. I know my typical 11-gallon fill-up is 210 lb of direct CO2 emission, 96 kg. That’s good for 420 or so miles of highway driving. Driving the 1,292 miles to Denver requires more than 3 tanks of gas — emitting almost 300 kg of direct CO2 emissions. 174 kg sounded like an emissions bargain.
Looking for corroboration, I was reminded of the adage, “A man with a watch knows what time it is. A man with two watches is never sure.” There were many calculators available to estimate the carbon emissions associated with my travel, but they varied widely in the answers given. Most didn’t fully disclose all assumptions, but some did. All included indirect emissions, something my comparison to driving ignores. Many of the calculators didn’t differentiate direction, using flight distance rather than duration in the estimates. The airline estimates varied with direction.
The flight time was shorter going east due to the prevailing winds. Less flight time, less fuel, less emissions. One estimated 365 kg each way, with others estimating 255, 250, 220, and 177, and 162 kg each way. The IATA estimator did differentiate by direction and gave the same estimates as the airline. None simply divided the actual emissions by the number of passengers to get the per passenger emissions. They all corrected for seating class with bigger seats being allotted bigger emissions. Two otherwise equivalent passengers on the same plane are allotted different emissions based on seat size. That both makes sense and is nonsensical. Accepting an upgrade to first class doesn’t change the plane’s emissions but would alter the fraction allotted to me. First class comes with 1.5 times the emissions of economy in most estimators.
Thanks to the friendly pilots, I know the actual fuel used — 13,500 lb to Denver and only 12,400 lb back. Each flight was full, so that’s 126 seats. The flights were responsible for an average of 153 kg and 141 kg per passenger of direct CO2 emissions, respectively, not accounting for seat class. More refinement is possible. My flight to Denver had several full-throated babies-in-arms near my seat. I didn’t add them as passengers. Doing so would reduce my part of the flight’s total emissions. I also didn’t account for seating class. That could, depending on assumptions, reduce my direct emissions footprint to 123 kg and 113 kg depending on flight direction. Flying, no matter how I calculate it, is better than driving.
Complaining about passenger air travel is easy. Erosion in the customer experience hides the advances in aviation efficiency that make air travel surprisingly environmentally friendly. Flights today, on a per passenger-basis, create 77% fewer emissions than those fondly remembered flights in the 1970s. Thanks to technological advances, my recent journey through the friendly skies wasn’t as bad as I feared.
Filed Under: Commentaries • insights • Technical thinking
