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adesso Blog

First, the facts

The Internet consumes energy. A lot of energy. If the Internet were a country, it would be third-largest consumer of electricity in the world, just behind China and the US.

Consumer association VerbraucherService Bayern [in German] states that an estimated 45 billion servers are constantly in use in data centres around the world. They also use large quantities of water for cooling in addition to the vast amounts of electricity they consume.

According to [in German], these data centres emit around the same amount of CO2 emissions as the global aviation industry. In 2018, there were more than 50,000 data centres in operation in Germany alone, consuming around 14 billion kilowatt hours of electricity.

This trend will continue in the coming years. The market is neither saturated nor lacking in new digital offerings. New technologies and increasingly data-intensive solutions are arriving at consumers’ doorsteps on what feels like a daily basis. Extremely high-resolution streaming, Internet of Things and many other services are pumped from the sender to the receivers via ever-higher bandwidths, estimated at 150,700 gigabytes – per second! Not to mention the energy and resources consumed in the manufacture and transport of the devices and the construction of network and server infrastructures.

What could be so bad about sending and receiving a few e-mails a day?

In terms of the individual user, it’s not bad. But on a global scale, the situation looks quite different. Market research company Statista assumes that around 333 billion e-mails will be sent and received every day in 2022 ( This number is estimated to rise to 376 billion in 2025. The tragic thing is that apart from the few actually relevant messages, it is mainly spam e-mails, newsletters, advertisements from online shops and notifications from social networks that are sent.

British newspaper The Guardian has estimated the amount of greenhouse gas emissions caused by e-mails:

  • 0.3 grams of CO2e per spam e-mail
  • Up to 50 grams of CO2e for an e-mail with a long and tiresome attachment

There are also plenty of other calculations that provide very similar results: according to VerbraucherService Bayern, ‘a normal e-mail without an attachment creates about 10 grams of carbon dioxide, which is equivalent to the carbon footprint of a plastic bag’.

How does this calculation come about?

An e-mail is created using a device – usually a computer, tablet or mobile phone. This device consumes electricity as it does so (not including the energy costs for production, retail and the delivery route to the consumer). When the e-mail is sent, it is then transmitted via a number of servers in order to reach the recipient. These servers also consume electricity – as does the communication between them (I’m not counting the water used for cooling here either). The recipient then also reads the e-mail on a device, which also consumes electricity.

But the most important point is that in the vast majority of cases, the e-mail remains unused on the server, and it constantly consumes power while in this state. The environmental impact for the mere provision of data that is not (or no longer) needed is referred to as ‘dormant pollution’.

Data storage generates the second-most CO2 emissions after data processing. A lot of energy is spent keeping these data graveyards alive. And even if you delete e-mails or other data, they don’t disappear immediately, but often remain as backups on the servers for many years and eat up electricity.

Even though spam e-mails account for a large part of global e-mail traffic, it is only responsible for about one fifth of the CO2 emissions of an average e-mail account. A large number of spam e-mails are already filtered out before they reach the recipient’s inbox, are deleted immediately or are never clicked on. E-mails with ‘legitimate’ content usually cause significantly more emissions because we spend longer on them and because they take up more storage space on average in the form of attachments. The Guardian estimates that the annual e-mail traffic of a business user creates an ecological footprint of 135 kilograms of CO2e. This corresponds to the greenhouse gas emissions of an average car driving for 320 kilometres!

The carbon footprint of an e-mail is 60 times smaller than that of a traditional letter. However, the number of e-mails sent today is much higher, it significantly exceeds the ecological savings effect and it ultimately even has a negative impact on the environment, which is referred to as the rebound effect [in German].

For example, if every adult in the UK were to send one ‘thank you’ e-mail fewer each day, this could save more than 16,000 tonnes of carbon dioxide (CO2) annually, says UK energy supplier Ovo Energy. This would equate to a CO2 effect of 80,000 flights from London to Madrid or of not using 3,300 diesel cars per year.

All in all, it makes for impressive reading. Everyone must decide for themselves whether refraining from politeness is the decisive lever for saving the climate.

So what can I do to make my own contribution to the climate?

There is a number of things you can do to help, which are listed below. They won’t have a major impact by themselves, but if everyone keeps factoring their own personal carbon footprint into their actions, we will start to see a significant improvement.

  • 1. Delete e-mails regularly – especially spam, newsletters and large e-mails to reduce dormant pollution
  • 2. Use data sharing platforms instead of sending attachments (Google Drive, Dropbox and so on) and if that doesn’t work:
    • a. Don’t send photos in high quality
    • b. Compress files before sending them (for example as a zip file)
  • 3. Shorten the recipient list
  • 4. Empty the Recycle Bin
  • 5. Set up a spam filter
  • 6. Unsubscribe from unused newsletter/advertising
  • 7. Turn off automatic notifications from social media (Facebook, Xing, LinkedIn and so on)
  • 8. Use an e-mail provider that operates its servers exclusively with green electricity. Link

And above all, maybe pick up the phone more often and, as well as clarifying open points, thank them for the information instead of sending a ‘thank you’ e-mail.

By the way, adesso has made it a top priority to reduce our company’s footprint by procuring energy exclusively from renewable sources, reducing the amount that our employees travel and lowering the CO2 emissions of our vehicle fleet. You can read more about this in our adesso sustainability report.

You will find more exciting topics from the adesso world in our latest blog posts.

Picture Tobias  Dieter

Author Tobias Dieter

Tobias Dieter has been working for adesso as a Managing Consultant in the areas of information security, IT service management and data protection since 2022. One of his main areas of work is the conception and implementation of security awareness campaigns.

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