The carbon footprint of emails
The number of emails sent is continuously increasing: While we were at 306 billion emails in 2021, numbers are expected to rise to 376 billion emails in 2025, researchers say. Whereas one single email does not drive carbon emissions up too much, it is the quantity that counts, researchers say.
In her approach of calculating the impact of email, sustainable content strategist Alisa Bonsignore points out the average email size to be 75 KB. If one large company (in her example a streaming video provider) sends out weekly newsletters to 200 million subscribers, the carbon footprint is as high as 360 cars driving for a year, she states.
The impact of email sizes and recipients
A 2019 study measured that the entire UK’s carbon footprint could be reduced by 16,000 t CO2, if every adult sent one less ‘pleasantry’ email every day just to say ‘thank you’ – as much as taking about 3000 diesel cars off the road. In total, over 64 million emails are being sent unnecessarily each and every day, oftentimes with no more than one word. Such an unnecessary email – one with up to four words – is estimated to account for one g CO2e .
The article of Walkley (2022) estimates a long email (three minutes read) to emit 17 g CO2e and a long email sent to 100 people to create 26 g CO2e. Spam emails caught by the filter account for about 0.03 g CO2e. Estimating that half of all emails sent are spam and the other half being emails of medium length, the carbon emissions of average email use correspond to driving a petrol-fuelled car for about 205 km (128 miles).
From the measurements in these studies, you can try and estimate your own emails’ carbon footprint. An easy way to reduce it can be avoiding short pleasantry emails.