A contribution by Rodrigo Gomes,
student at Nova School of Business and Economics, Lisbon,
on exchange at ESSCA in 2018.


Everyone is aware of online shopping causing transport emissions. Everyone is careful about, or at least aware of wasting paper. But no one ever thinks about the environmental impacts of sending an email. Neither did I until I have heard of it in class. First, I was a bit sceptical about how many grams of CO2 an email could produce. Even more disbelieving when a comparison was made to the CO2 emitted in a car trip. How could an email be worse than my car trip to school? This made me look for detailed information and find interesting things that I’ll share in this post.

Email has become one of the most important ways of communication over recent years. According to statistics more than 3.8 billion people have an email account, which stands for 50% of the world’s population. The number of global users is expected to increase by 3% every year, which can be translated into 246 billions of emails sent/received daily in 2019, a ten-billion rise from this year. In the business world, statistics show that an average office worker receives 123 and sends 35 emails per day (average of the values found during the research).

Global spam volume as percentage of total e-mail traffic from January 2014 to March 2018, monthly.

Regarding the Spam mails, although they tend to decrease over the last months as observable in the graph, they still account for around 48,2% of the total sent emails. For a message to be considered spam it must have two characteristics: first, it has to be sent as part of a large collection with similar content, for example newsletters. Moreover, it must be an unrequested email. Only when meeting these two criteria they can be classified as spam. Nowadays, our mail boxes are quite good in filtering incoming emails, consequently the greater part never gets to your inbox, so you don’t have to lose time with it.

According to the specialist Mike Berners-Lee, even if they are not opened, spam mails emit 0,3 grams of CO2 to the atmosphere. Now that you know the share of spam emails and their contribution in carbon terms, you can start doing some maths concerning the useless emissions our generation produces. Experts estimate Spam Mails’ annually electricity consumption of around 33terawatt hours (TWh), equivalent to the greenhouse gas emissions of 3.1 million passengers cars using two billion gallons of gasoline.

The 0.3 grams come from the energy spent running the computers, using the internet and the whole physical system and infrastructures behind, including storing and transmitting the information through data centres. Taking this in consideration we can easily conclude that real emails, the ones we pay attention to and take time dealing with, will have a higher footprint. If we think about the 35 average emails sent by the office worker and multiply by the 4 grams which a proper email generates, we will overcome the approximately 120 grams of CO2 released in one kilometre trip on an average sized car (average of diesel and petrol cars emission in 2017).

And that’s not the worst: according to the scientists, an email with a long text and an attachment can stand for 50 grams of CO2. For the same average sized car, it would now be 2,5 emails. Have you ever thought you could be polluting the same amount by pursuing these two activities? For more detailed information on the topic and other activities’ carbon consumption check this article.

Having understood the whole consumption system behind email you may now depict some linear inferences about social networks and their carbon footprint considering the amount of text, pictures and videos we share every single day. Given the size and importance of this topic it is not possible to cover it in this post but mentioning it may arouse some curiosities about. One thing you may conclude by your own is that social networks using videos and photos will have a higher impact than others using text. Check here the Facebook’s effort to decrease their carbon footprint.

Sending and receiving electronic messages will never be our major priority to avoid the greenhouse effect. But if at least we had a way to avoid spam we would already cut unnecessary emissions. The question has been addressed through the years, but there is still no answer for this problem. At the same time the experts fight against this abuse, exploiting new systems, the “spammers” do the same in the opposite direction. The question is not only environmental, it also leads to economic and social costs. The problem is global, the costs are global, therefore the interest to end up with Spam mail is also global.

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