What is more sustainable: an email or an instant message?

Blurred greenery and cell phone screen with green icons of message apps evoking the question if the messages are sustainable

Messaging, as clean and green as it seems, actually has a carbon footprint

Billions of emails and messages are sent worldwide every day, and sustainable effect is the last thing we consider because online activity leaves no reason to think about the eco-practices (but not in ATRIUM!). What if we told you that messaging, as clean and green as it seems, actually has a carbon footprint?

Worldwide, the use of mobile messaging and social apps (instant messages) is growing at a higher rate than any other mobile apps. The most popular messaging app in the world is Whatsapp with 2.24 billion monthly active users in January 2023. Facebook messenger, the Chinese services QQ mobile and WeChat make up for the remaining top 3. As a result, the popularity of SMS has been decreasing.

Cell phone with message apps in front of a laptop with email on the screen
Photo: Unsplash

On the other hand, 333,2 billion emails were sent and received in 2022 worldwide. It is estimated that in 2023 the number will be 347,3 billion.

All these communications mean that there are plenty of data flows taking place. Data flows consume energy and therefore, release CO2. So from an environmental perspective, it’s interesting to know what’s the most sustainable option. Should we use SMS, an instant message via an app or send an email? What’s is the most sustainable option?

Sustainable forest screensaver on monitor and computer mouse on a light table
Photo: Unsplash

Messages and emails: different technologies – different impacts

Sending an email, SMS or instant message has an environmental impact because the cell phone or the computer needs electricity to work and to be able to send a message, but the energy needed to manage, transport, and store this data is what has the biggest ecological impact.

An SMS, an instant message or an email don’t share the same environmental impact. This happens because they don’t use the same technologies. Whereas SMS use the frequencies of conventional telephony, instant messages and emails use internet data flows. These are different ways of processing data that spend different amounts of energy.

Cell phone onto white keyboard as an illustration of a question: what is more sustainable - an email or a message?
Photo: Unsplash

The carbon footprint of messages and emails

Mike Berners-Lee wrote a book named “How bad are bananas?”. In this book, he talks about the environmental footprint of “nearly everything”. And he does it by presenting the different carbon footprints of various products. Some of Berners-Lee calculations reveal that an average email emits 4 g of CO2 and an SMS emits 0.014 g of CO2. He used data from cell towers, data transfers and data centers for his maths. Other researchers, like Frédéric Bordage from GreenIt.fr, estimate that an SMS with a maximum weight of 140 bytes emits 0.00215 g of CO2 (based on the data provided by Vodafone). Hence, we can say that SMS uses less energy and emits less CO2 than emails.

Regarding instant messages, there are less concrete data yet that allows its carbon footprint to be predicted. However, since these communications use Internet networks, it’s reasonable to think that their carbon footprint is closer to the one of an email than to an SMS.

A recent study conducted by the French researcher Basile Fighiera shows that, nowadays, an email with a 1MB document attached, sent using Wi-Fi, will emit 3.3 g CO2e. A short message without attachments sent to 10 recipients will emit 4.9 g CO2e.

The world’s text messaging exchange is estimated to emit 32,000 tons CO2e per year. This carbon footprint is very small when compared to humankind’s total carbon footprint: 40 billion tons CO2e per year. But we believe that when it comes to protecting our planet, every step towards cleaner practices – small and big – count.


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