a3nm's blog

Estimating carbon footprints: what is 1 ton of CO2e?

I just posted an article on the blog of the TCS4F initiative about how to understand the carbon footprint of various kinds of activities. You can read it here: Estimating carbon footprints: what is 1 ton of CO2e?.

Writing this kind of posts is a bit hard for me, because I'm certainly not an expert on climate change, so I don't feel very legitimate and hope that what I am saying there is realistic. Still, I hope that doing my own statistics is better than being completely in the dark. Anyway, reading about all this was the occasion to discover many surprising things about my own footprint, which can help me focus my efforts on the right areas. Personally here were the surprisingly high numbers, based on figures from the post:

  • The plane trips I take (most of which are for work) probably have a carbon footprint which is greater that all my other sources of emissions combined: several tons of CO2e per year, if not dozens of tons1. So this was the main take away: the number one area on which I should work is on travelling less to distant places : avoiding a transcontinental plane trip saves tons of CO2e emissions.
  • The carbon footprint of heating my flat (collective heating) is already about 1.2 tons of CO2e per year. Probably a bit less overall than the footprint of the food I eat, but certainly not negligible, even though I don't think much about it and have little control over it...
  • In a sense, the few Bitcoin transactions I have done last year may have ended up corresponding to several hundred kilos of CO2e on their own. I would never have guessed.
  • Not using a car probably allows me to save around one ton of CO2e per year in emissions from fuel for my commute, and several additional tons in terms of not having to produce the car.

And here were the surprisingly low numbers:

  • Avoiding meat only saves around 600 kg CO2e per year. Not negligible if everyone does it, but certainly small compared to the impact of a single long plane trip. Also, the food to avoid most is unquestionably beef, and avoiding non-local food (e.g., bananas) is certainly not worth it (see this study). So I'm still onboard with reducing my meat consumption, but transgressing every now and then isn't probably so much of a deal.
  • The carbon footprint in France is really low, thanks to the predominant use of nuclear power (not to mention other environmental costs, of course), so my total consumption of around 1800 kWh per year only represents around 18 kg CO2e.
  • Likewise, I was surprised to see that the estimated CO2e footprint of producing a mobile phone is only around 80 kg CO2e, and producing a T-shirt is only around 7 kg CO2e. Again, this says nothing of other environmental costs, but it is lower than I would have expected. I'm still not a fan of buying new hardware just for the sake of it, but apparently it's not such a huge deal in terms of greenhouse gas emissions.

I encourage you to read the post, which can hopefully give you a better idea of how your activities are producing CO2e, and what's the best way to help by reducing your emissions. And of course I'd be delighted to hear back if you have questions or comments about the results.


  1. I even went as far as trying to list all flights I took in my life, which wasn't so hard (took about an hour, if I didn't forget any). There are 125 flights, amounting to a total of 408 thousand kilometers, i.e., going over the world 10 times in total, or a bit over a one-way trip to the moon (!). This probably represents around a hundred tons of CO2e which is commensurate to a total sustainable lifetime carbon budget, except I'm only 30... One surprising point was that over half of this total is consumed by the 20 longest flights, so the biggest culprit is really long transcontinental trips. 

  2. In fact, I am a proud subscriber of Enercoop (in French), which means that in a sense I am already offsetting the footprint of my electricity consumption. 

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