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The best way to fly

Posted at 2022-09-05 18:58:01 by Ditte

In this blog we want to go away from the food theme. Our site is about our everyday life and food is obviously a major part of this, but energy and transport also play a big role.
Most people probably know that flying is one of the least sustainable modes of transport. Therefore, we were really conflicted when we received an invitation in April, for a wedding two months later from a good friend living in Mexico. Long story short we concluded we would regret not going to the wedding and therefore began to research possible flights!

UPDATE - 21.09.22 The majority of this blog was written several months ago. During this period it has come to our attention that Google flights have change their calculation methods and are they are currently not including non-CO2 pollutants such as contrails. These non-CO2 pollutants still has an effect on global warming and should be accounted for. Furthermore, the impact from the non-CO2 pollutants can vary according to flight altitude and time a day and therefore it can heavily impact the end results. We choose to keep our blog as it is, because we think the message is still the same. One should inform themselves, when making a choice. You can read more here.

But how to choose the most sustainable flight connection? We were very happy when we found an affordable non-stop connection from Germany to Mexico. We thought “wow”, with a short notice we can make the most sustainable choice and not even break the bank. In order to check the flexibility and get an overview of selection, we went to google flights. In addition to having a wide selection of airlines they also inform about the amount of CO2e each flight emits and if it is higher or lower than average. To my big surprise and against what most articles on the world wide web write, my initial found non-stop flight was not the most sustainable connection at all. In fact for many cases it was just as bad as some of the flights with two stops.

This blog was written some months after buying the ticket, so I cannot find the concrete flights we were investigating, but I tried including some examples from google flights that show the explained cases.

All of the below examples are based on 1 person in economy class.

Munich - > Cancun

2 stops British Airways 1 stop United Airlines 2 Stops British Airways 1 Stop Delta airlines
533 kgCO2e 951 kgCO2e 753 kgCO2e 524 kgCO2e

We also wanted to check that this was not just a one time thing, between Germany and Mexico. So we decided to also include a route to Asia.

Frankfurt - > Taipei

Non-stop China Airlines 1 stop EVA air 1 stop Singapore airlines 2 stops EVA air
662 kgCO2e 541 kgCO2e 941 kgCO2e 661 kgCO2

You can also see here that even between airlines the emissions can be different. So I looked into the methodology that google flights uses. According to google flights website they use the European Environmental Agency (EEA) emission estimates with the most up-to-date algorithmic model from 2019. The model takes into account the different fuel consumption during the various phases of flight taxi-ing, takeoff, climb, cruise, descent, approach and landing. I recommend you also have your own look into the method of google flights and the EEA algorithm google explaining their method.

The input is based on the aircraft type as well as the seating plan.

There are several factor that will influence the emissions from a flight:

  • Aircraft model and configuration
  • Speed and altitude of the aircraft
  • Distance between origin and destination

With all these factors playing a role, it will not be sure that non-stop flights are less polluting. Especially on long distance flights, where fuel efficiency plays a major role. Moreover, even aircrafts with a similar capacity can emit different amounts per passenger, if the seating plan or aircraft type differs.

I wanted to bring this information forward, since it seems like there is a misconception that non-stop flights are always the most sustainable option, because most fuel is spent on descension and landing. In many cases it will be a good choice to choose a non-stop flight, but sometimes it might end up having even double the emissions of a one stop connection.

Obviously, Google uses an algorithm that is also based on estimations and if you book your flight half a year in advance the aircraft type could still change. However, I still believe it gives you a very good indication and helps you as a consumer to be informed and make a conscious choice.

Flight vs. bus

Furthermore, we had a very great experience travelling in Mexico. To get around we used mainly buses. Unfortunately, for many destinations in Mexico it is cheaper taking the plane than taking the bus and our Mexican friends thought it was strange we would even consider spending so much time on the bus. We personally love the bus trips and seeing how the landscape changes as we progress. But how much emissions do we actually save in comparison with taking the flight? I took the average emissions from google flights and compared it with the average emissions factor of coach travelling from the website carbon independent. Furthermore, I also included the ranges of emissions, which depends on which sources or flight you take.

Route Flight emissions (range) [kgCO2e] Flight emissions (average) [kgCO2e] Distance on land [km] Coach emission (range)[kgCO2e/pers/km] Coach emission (average)[kgCO2e/pers/km]
Mexico city -> Oaxaca 42-97 62 460 12.88-40.94 30.08
Oaxaca -> Guadalajara 94-142 108 1015 28.42-90.34 66.38
Guadalajara -> Mexico city 40-55 46 550 15.4-48.95 35.97
Total 172-294 216 2025 56.7-180 132.435

Potentially we have saved about 238kgCO2e by choosing bus over flight, but worse case we did not save anything, which I truly hope and think is not the case. I expect the truth lies somewhere in between. I can only conclude that neither modes of transportation are good for the environment. However, when travelling I can only encourage keeping yourself informed and try to make the best choice fitting to your needs, wallet and conscience.