A lot of us travel around this time of year. A few months ago, I had to go to California. I was certain driving would result in a lower carbon footprint than flying.
According to the New York Times, one round-trip flight between New York and California generates 20% of the greenhouse gases that your car emits for the entire year.
Overall, the aviation industry accounts for 11% of travel-related emissions in the United States. Globally, there are now over 100,000 flights daily (according to The Guardian). That number is expected to double in the decades ahead.
So, should you fly or should you drive? For business travel, you often don’t have a choice; you have to get there as fast as possible. But how about for optional trips and recreational travel. Isn’t it better for the environment if you drive?
Research by Michael Sivak of the University of Michigan Transportation Research Institute determined that the average fuel consumed per passenger mile on airplane travel was 2033 BTUs (British thermal units). In contrast, the average for cars is 4211 BTUs per passenger mile. How is it possible that driving has twice the carbon footprint as flying?
According to Sivak, “Flying domestically in the U.S. used to be much more energy intensive than driving, but that is no longer the case. One of the main reasons is that the proportion of occupied seats on airplanes has increased substantially, while the number of occupants in cars and other light duty vehicles has decreased.”
These numbers are based on vehicles that get no more than 22 miles per gallon, so include SUVs and small trucks. They also assume that there is only one individual in each car. The numbers change if you’re driving a car with better gas mileage. My car gets 38 miles per gallon on the highway. Hybrids can get 50 or 60 miles per gallon. And if you have a passenger or two, it is better to drive.
If you are planning a trip, you can calculate the carbon footprint of your travel on numerous internet sites, such as myclimate.org, nature.org, coolclimate and carbonfootprint.com.
Rutherford and Kwan of the International Council on Clean Transportation say that “if you’re driving a hybrid and have some passengers, you’re going to be four to five times more efficient than a plane over a similar distance.” So, use your most energy-efficient car for family vacations.
There are other considerations in addition to carbon dioxide. The International Panel on Climate Change points out that aviation emissions also include water vapor, which creates clouds and releases black carbon, nitrous oxide and sulfur oxide into the high atmosphere, thereby trapping heat. The contrails and clouds produced by the plane’s wastewater vapor are short-lived, but have not yet been adequately researched.
Some airlines are now adding biofuel to their mix to reduce emissions. According to the Energy Transitions Commission, in the future, commercial airlines may be powered by synfuel, biofuel (including algae), electric batteries and hydrogen.
There will also be significant future fuel efficiency gains with new airplane designs and systems. But none of that is happening any time soon. The technology just isn’t there yet.
In the meantime, the most efficient way to reduce your carbon footprint is to fly less often. Direct flights have a lower carbon footprint.
According to NASA, 25% of emissions come from landing and takeoff. First-class seats have a carbon footprint nine times as large as the economy seats because so few people are being moved by the same amount of fuel.
Fuel efficiency varies and you can check it online. According to the International Council on Clean Transportation, American Airlines and Allegiant are at the bottom of the list. And if you decide to drive rather than fly, use an efficient vehicle and take passengers.
My California trip, by air, was a bust. The flights were delayed. I got in eight hours late in the middle of the night, ragged and exhausted. The next time I have to go to California, I will drive and hopefully take a passenger or two. It would even make sense to rent a Prius.
Judith Polich, a longtime New Mexico resident, is a retired attorney with a background in environmental studies and is a student of climate change. She can be reachd at firstname.lastname@example.org.