Carbon cost of email (part two)
Digging further into the carbon cost of emails, I take a look at the numbers that underpin the discussion.
This is the second part of a series on the supposed green benefits of deleting email. Part one is here.
As I said in the first article my IT department has made the claim that deleting 1GB of old emails can save 3-7 kilowatt-hours of electricity per year. Obviously they've not calculated that themselves but instead directed me to an article from the Carbon Literacy Project which didn't answer the question but nevertheless did have some dubious statistics of its own.
According to the Carbon Literacy people, receiving emails for a year produces a carbon footprint of 0.6 tonnes of CO2 which they helpfully compare to the carbon footprint of the average Indian citizen of 1.5 tonnes. This leads to the claim that the email received by three people releases as much carbon as one other person's entire life.
So where do they get their figures from? The answer is a book called How Bad are Bananas?: The Carbon Footprint of Everything by Mike Berners-Lee (younger brother of world wide web inventor Tim). And they're not the only ones basing their claims on Mr Berners-Lee's book. Pretty much every website I found that mentioned the carbon cost of email was either directly or indirectly referencing the numbers in How Bad are Bananas? No pressure, Mike, but your figures seem to be a bit load-bearing in this discussion.
Possibly the most egregious use of the Bananas data came in a 2019 press release from the UK energy company OVO. They claimed (and were quoted in many news outlets at the time) that "if every Brit sent one less thank you email a day, we would save 16,433 tonnes of carbon a year – the same as 81,152 flights to Madrid". To give OVO some credit they did at least show their working for this claim :
- 64,317,204 unnecessary emails sent by Brits every day
- x1 email = 1g carbon = 0.000001 tonnes CO2e per email (Source: Mike Berners-Lee)
- 64,317,204 x 0.000001 = 64.317 tonnes CO2e per day
- 64.317 x 365 = 23,475.779
- \= 23,476 tonnes CO2e per year
It's worthwhile to read the detail of "1 email = 1g carbon" in Berners-Lee's book:
The footprint of an email comes from the electricity needed to power the kit used at each stage of the process: the device it is written on, the network that sends it, the data centre it is stored on and finally the device that you read it on. The devices at each end are the dominant factors, even if you send big attachments ... the embodied emissions of a smartphone represent 84 per cent of a short email’s carbon footprint. That percentage would be higher still for a laptop, and a step up again for a desktop computer.
In other words, most of the carbon is not generated by the email per se but by the physical hardware that is used to transmit it and much of that is a fixed quantity from the manufacturing of the hardware in the first place. He goes on to note that "genuine [non-spam] email has a bigger carbon footprint simply because it takes more time to deal with". It's the human being sitting at the computer or staring at their phone that is creating demand for electricity and if they weren't reading an email they'd probably still be using that device for something else.
In the 2020 updated edition of his book Mike Berners-Lee actually mentions this press release and the fact that he supported it in raising awareness of the carbon cost of everyday life. He notes though that "the actual carbon to be saved from reducing the smallest emails of all is tiny – and it can also be wonderfully important to say thank you".
Which leads to my next point : reducing email traffic is one thing but what is the alternative? Composing, transmitting and reading an email produces one twentieth of the carbon emissions involved in sending a letter by post. A Zoom call can release as much as fifty grams of CO2 an hour but if the alternative is taking a flight to meet in person then that is on the order of tonnes of carbon. Sure we could massively reduce our carbon footprint by going back to living in wooden huts and giving up the whole notion of modern life (and some people would argue that that was a good idea, especially if they've been stuck in a Zoom call all day) but is that a sacrifice we're prepared to make?
In part three of this series I'll be answering the question "why does this matter? So what if people are sharing dubious advice about the environmental impact of email?"
How Bad Are Bananas
Read more about the carbon footprint of everything in Mike Berners-Lee's book ( Full disclosure: as an Amazon Associate I earn from qualifying purchases )
