How green is my aircraft?

As I have mentioned before, this is a busy time of year for me. A lot of my time is spent flying places. Well, actually, the bulk of the time is spent waiting for a plane or sitting on the thing waiting for it to go somewhere. In other words, there is lots of “idle” time. I spend that time in various ways. Firstly, there is eating and drinking – first rule of business travel is “eat when food presents itself – you never know where the next meal is coming from”. I spend some time working and I enjoy reading. [But why can I not use my Kindle except when the seatbelt sign is off? Does anyone know?] I also spend my time thinking.

A recent train of thought was “just how environmentally unfriendly is all this flying?” …

We are always told that it is not green to fly – aircraft engines contribute massively to carbon dioxide dumped into the atmosphere. I have no doubt that this is true. I am certain that those who deny the existence and significance man-made climate change are deluding themselves. However, what I wanted to know is just how bad is flying, from an environmental perspective?

What I wanted was some figures that I could understand and relate to. I had seen reports of how many tons of carbon dioxide are emitted, but the numbers did not make much sense to me. Then I found some statistics that gave me a basis for understanding. I was glancing at the in-flight magazine [must have been during the Kindle blackout period] on a Scandinavian Airlines flight, reading the specifications for their fleet of aircraft. [See how boring it can get!] This included the fuel consumption, which I thought must a be clue to environmental impact.

I understand that fuel consumption is not the same as carbon dioxide emission, but it must have some bearing. I also appreciate that aviation fuel is different from the gasoline or diesel that we put in our cars – it has a different calorific value and the exhaust gas probably contains a different proportion of carbon dioxide, but I felt that these fuel consumption figures give us something to work with.

There were 10 models of plane listed – mainly Boeing and Airbus models, but there was also an MD-82 [which I guess is a much older and less efficient model]. The fuel consumption was quoted in liters per seat per kilometer. The lowest value was 0.028 for a Boeing 737-800 and the highest was 0.041 for the MD-82 [no surprise there]. I noted down all the figures and put them into a spreadsheet, which enabled me to translate to miles per gallon [I used US gallons – UK readers need to multiply by 1.25]. This yielded figures of 80mpg and 55mpg respectively.

These numbers compare favorably with a car. My car delivers around 40mpg, for example. I appreciate that these numbers are likely to relate only to the plane running with an optimal passenger load [probably full], but it should also be borne in mind that aircraft fly in fairly straight lines [compared with a car’s typical route]. So, my conclusion is that flying is not quite so bad after all. If you can suggest a serious flaw in my logic or calculations, please email or comment. If you want a copy of my spreadsheet just say.

I am sometimes told by those close to me that I think too much. To quote an old English saying: “Sometimes I sits and thinks. Other times I just sits.” Good advice perhaps.

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  • Colin, you’ve disturbed my “just sitting” into “sitting and thinking”… is a logical flaw that if your flight on Scandinavian was from the UK to Sweden (just my guess) you’d find it hard driving that route in your car? London to San Francisco would be even more challenging. Perhaps comparing planes with the new generation of airships I hear about might show planes in a worse light. Another thought – I guess that most of the “stuff” transported around the world is goods, not humans (ie “trade”), and if you include all business human travel as part of “trade”, then everytime we read headlines of “global economic downturn”, this implies relatively good news for the planet. So if we trade and travel a lot we heat up a lot?

  • I agree that driving to San Francisco would be challenging [though not from where I’m sitting at this moment]. Stockholm would be OK – just need to cross the Channel somehow.

    I agree about economic downturns – good for the planet. I do dismay when I see packs of vegetables that have been shipped thousands of miles, but are also grown just down the road.

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This article first appeared on the Siemens Digital Industries Software blog at https://blogs.sw.siemens.com/embedded-software/2011/10/20/how-green-is-my-aircraft/