How to cut your emissions when traveling by air

But have you thought yet about how you're getting to and from the airport? Your choice could have a significant effect on the overall carbon emissions from your trip.

A few weeks ago, my colleague Michael Brylawski wrote about the environmental impacts of flying. In the post, he cited a greenhouse gas inventory compiled by Seattle-Tacoma airport, which is pretty consistent with what other airports around the world are finding.

The gist: Roughly 90 percent of all emissions from flying are generated by the airplanes; 2 percent comes from the airport itself; and the remaining 8 percent from people getting to and from the airport.

As Michael commented, it's unlikely that you're going to be able to influence the emissions from the plane. Most of us choose itineraries based on price and schedule, not whether we're flying the most fuel-efficient jet.

Similarly, there's not much you can do to reduce emissions at the airport, since that has mostly to do with how the terminals were designed, the types of ground equipment the airport uses, etc.

But that 8 percent -- how you get to and from the airport -- is in your hands.

So as your vacation approaches, take a second look at your options. I've arranged them here from best to worst:

Ride public transit
This is by far the best option, environmentally speaking, because you're sharing the ride with dozens of other people. In addition, many public transit systems now run on cleaner fuels such as compressed natural gas or low-sulfur diesel.

Even if public transit takes a little longer, it's bound to cost less than any of the other options. And with great online tools for finding the best route and timetables, there's little reason to pass that bus or metro ride up. 

Take a shared-ride van
Most airports are now served by shared-ride vans. These are generally more environmentally friendly than driving yourself because they increase the "passenger miles per gallon." That is, they move more people per gallon of gas burned.

So even if the fuel efficiency of that van isn't great, it usually beats taking a taxi or driving yourself. Who knows? You might even meet someone friendly on the ride. 

Drive yourself
It may seem counter-intuitive, but driving yourself to the airport is less carbon-intensive than having someone else drive you. That's because you're eliminating at least two (and potentially four) unnecessary trips. If a family or friend takes you to the airport, s/he has to drive back home afterward. If someone comes to pick you up when you get back, that person has to make that extra trip out to the airport.

Assuming that this happens at both ends of your flight, you're creating four unnecessary trips.

Hop a taxi
This might be a toss-up with driving yourself, because taxis tend to pick people up for both legs of an airport run. But unless you're in a big city, it's unlikely the taxi driver will be able to pick up another fare immediately after s/he drops you off at your home. That means there might be a few unnecessary miles driven. Still, if you can take a hybrid taxi, like the ones in New York City, you're miles ahead.

Have someone drive you
This is the worst option, because it potentially creates four unnecessary trips as described above.

So tell Mom it's okay if she doesn't meet you when you step out of baggage claim. By getting to and from the airport by any other means, you're cutting your overall air travel emissions.

Noah Buhayar is a fellow at Rocky Mountain Institute.