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The hidden environmental cost of your overflowing email inbox

A man uses a computer keyboard in Toronto, Monday, Oct. 9, 2023 in this photo illustration. THE CANADIAN PRESS/Graeme Roy

When consumers think about ways to reduce their carbon footprint, lowering their car usage, eating fewer animal products and reducing their waste likely come to mind. 

But there’s another, perhaps easier, way to cut your emissions: delete old emails. 

Your overflowing email inbox is a lesser-known climate villain, consuming energy and collectively producing hundreds of thousands of tonnes of carbon dioxide every day for years, even decades.

Last year, 4.2 billion email users sent and received 333 billion emails a day, a number that’s expected to hit 400 billion by 2026, projections by Statista suggest. Meanwhile, the data centres and servers that transmit and store each email consume significant amounts of energy. 

However, the energy and environmental costs associated with emails are little studied, according to Mike Berners-Lee, a U.K.-based carbon footprint researcher at Lancaster University.

The electricity used by emails results in a wide range of CO2 equivalent: from 0.05 grams for a spam email picked up by filters to 29 grams for a long email sent to a 100 people, his estimates show.

It factors in electricity used to power the device on which the email is written, sent and received, length of the email, number of recipients and the power consumed by the network and data centres used in the process.

A typical user receives about 75 emails daily, averaging 1.38 grams of CO2 equivalent each and producing a yearly carbon footprint of 38 kilograms, the equivalent of driving 200 kilometres in a small gasoline-powered car, according to Berners-Lee's estimates. 

On top of that, the cost of storing emails long-term largely remains a mystery.

An email can live for years and major email service providers such as Google and Microsoft have never disclosed how much power they use to maintain emails in their data centres. 

Microsoft declined an interview request and Google did not reply to questions about the volume and age of emails stored in its data centres and the associated carbon footprint.

Overall, however, global data centres consumed roughly 340 terawatt hours in 2022, according to the International Energy Agency. That’s enough to power New York City for six years. 

For consumers and businesses looking to reduce their environmental impact, there's no simple solution because email use is so widespread.

“There's this status quo bias that for a behavior to change, we need a new incentive,” said Nir Eyal, an expert in behavioural design and the author of Hooked.

“Things will keep going the way they are unless there's some new momentum, some new action to precipitate that behaviour. So, when it comes to email in users’ minds, there's really no benefit to deleting the email that can outweigh the cost.” 

Emotion also plays a role in email archiving, says Amber Cushing, associate professor at University College Dublin, who focuses on the context of maintaining digital information over time. 

“People get meaning out of keeping an email. Maybe it is from a close family member, or it represents a relationship to someone. Maybe the relationship is ongoing, maybe the relationship isn't anymore. Maybe it's a family member who has passed away and there's sort of a memory memento aspect to it,” she said. 

Any broad-based solution to the problem of email-related CO2 emissions will likely need to come from major service providers such as Google and Microsoft, since they account for so much traffic. More power-efficient data centres and users’ education about email management best practices are the easiest early answers, Eyal and Cushing say. 

Artificial intelligence could play a role by helping users better manage emails with AI-trained virtual assistants that can sort emails by importance, effectively creating a discard pile.

Microsoft’s Copilot AI assistant, released in November in its enterprise suite of office applications like Outlook and Word, and Google’s move in September to connect its Bard AI with Gmail, are steps in that direction.

Which makes sense to Eyal.

“The average consumer is just trying to raise a family and pay their bills. ... It's much easier to have the email service provider figure out how to green the solution versus asking customers to change their behaviour,” he said. 

Meanwhile, these good habits are the foundation for email users seeking to take immediate action about the carbon footprint:

— Use the right communication app for the context: Instant messaging for things that won’t need saving, such as quick questions at work, or “I’m running late” messages. 

— Use a self-deleting function, such as the ‘disappearing messages’ option in WhatsApp. 

— Archive your stored emails. It compresses and reduces their size in the cloud so they need less power to live on. 

— Avoid reply-all. Only send email to people who need to see it – fewer people means fewer devices, less email network traffic, less electricity used and fewer emissions.

This report by The Canadian Press was first published Dec. 1, 2023.


Ab Nacef is a freelance reporter. He is director of program management at Advanced Micro Devices and currently a fellow in the Dalla Lana Fellowship in Journalism and Health Impact at the University of Toronto.

Ab Nacef, The Canadian Press

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