sending one less email per day saves 16 tonnes of CO2?

Should we send fewer emails to fight against global warming? As winter approaches, faced with the energy crisis, the government encourages the French to reduce their consumption. Among the recommended gestures: lower the heating to 19°C, set your water heater to 55°C, program your washing machines in the afternoon or at night…

In May, Agnès Pannier-Runacher, the very recent Minister for Energy Transition, mentioned another eco-gesture, on BFM. “We are going to turn off the light thinking that we have made big energy savings and we are going to send a slightly funny email to our friends with an attachment and we will have consumed a lot more energy”, she said. Is it really an effective gesture?

In the United Kingdom, the energy supplier OVO Energy published in 2019 a study (in English) concluding that if every Briton sent one less email per day, CO2 emissions would fall by 16.433 tonnes per year. This figure (which only concerns the United Kingdom in 2019) circulates in France, with an additional approximation in the translation. You can read there that “deleting an email is equal to 16 tonnes of CO2 saved”instead of “delete an email sent”. These 16 tonnes saved are equivalent to “16 round trips Paris-New York”can we read on an infographic shared on Twitter and LinkedIn.

“An email pollutes as soon as it is sent, by its journey on the networks”explains Francis Vivat, research engineer at Atmospheres, Environments, Spatial Observations Laboratory (LATMOS) affiliated to the CNRS. Sending an email consumes energy by soliciting the sender server and the receiver server through which it passes. This impact may vary depending on the number of recipients and the size of the attachments but also on the energy mix, if the electricity consumed is produced by means of production with high CO2 emissions, such as coal-fired power plants. To this must be added the pollution generated by the time taken by the various interlocutors to write the email and read it on a computer or mobile.

Deleting an email is also a polluting activity, points out Frédéric Bordage, founder of the Green IT collective which brings together sobriety experts. “Time Spent For Deletion” cancel the benefit “of the avoided impact of storage”warns the expert.

According to the OVO study, it would be possible to reduce CO2 emissions related to emails just by avoiding sending thank you emails. Each day, “64 million useless emails” containing only the words “Thanks” Where “Thank you” are traded in the UK, according to this 2019 study.

While it is difficult to accurately measure the environmental impact of a shipment, estimates are based on often questionable methodologies according to the GDS EcoInfo, a group of environmental experts affiliated with the CNRSsaccording to the English journal specializing in the environment Carbon Literacy, the carbon footprint of an email can vary from 0.03 g to 26 g of CO2 (for an email sent to 100 people). A short ‘thank you’ email generates well “around 1 g of CO2 equivalent”, specifies the expert in digital pollution Frédéric Bordage. If a user sends one less per day, he avoids the emission of 365 g of CO2 per year. Multiplied by the number of adult Internet users in the UK (just over 45 million, according to OVO), this saving can enable a reduction of 16,433 tonnes of CO2 for the whole of the UK, effectively the equivalent of the emissions 16 Paris-New York round trips (one round trip generating one tonne of CO2, according to Civil Aviation).

The carbon impact of a reduction in the sending of mail is, however, “epsilonesque” compared to other sources of pollution, judge Frédéric Bordage. If avoiding sending an email is a gesture “positive” for the environmental expert, emails are “The tree that hides the forest” of the footprint generated by the production of the devices. “In the case of a smartphone kept for three years, 80% of the emissions are produced during its construction and 20% during its use”, abounds Didier Mallarino, CNRS research engineer at OSU Pythéas and co-director of GDS EcoInfo.

“The footprint of all emails sent by a professional for a year amounts to 75 kg of CO2 while buying a second screen generates 530 kg of CO2”, adds Frédéric Bordage. It is therefore necessary rather “extend the life of equipment and avoid over-equipping” to effectively reduce digital pollution, judges the founder of Green IT.

Among the uses, sending mail is not the most polluting either. “Email represents a relatively insignificant part of all digital uses”, insists Didier Mallarino. “If we do a top 10 bandwidth usage, the emails don’t appear there”, assures Emmanuelle Frenoux, lecturer at the Interdisciplinary Laboratory of Digital Sciences (LISN) at the University of Paris-Saclay. The three most important uses are “streaming (60% of traffic), web browsing (13%), gaming (8%)”.

Limiting yourself to sending fewer emails can be a way of “getting good habits” judge however the university. “If we start to wonder if it is useful to send a thank you email, we can hope that we will also wonder if it is necessary to watch videos of kittens on YouTube”. According to think tank The Shift, watching videos online is responsible for almost 1% of global CO2 emissions (PDF).