I’ve said it myself a hundred times: “Save the paper—just email me the receipt.”
This past week, however, some shocking numbers came to light concerning the digital carbon footprint associated with our email-happy world, giving me pause to reconsider.
For those who haven’t been keeping up, a digital carbon footprint refers to the environmental impact of digital technologies and online activities, including greenhouse gas (GHG) emissions and the consumption of energy associated with use and operation of digital devices, networks and services.
As an example, storing 1GB of data consumes an average of 0.015 kW of electricity, resulting in 0.28 kg of CO2 equivalent (CO2e) in emissions—meaning the photos on my phone alone account for a kilo of carbon. When it comes to email, CO2e is universally pegged at about 0.3 gm/email—about a third of a gram. This formed the basis for a recent study by Zero Bounce—a commercial email validation service—of global email use (data from the top 27 email countries listed here: rb.gy/mexqqg).
Among the findings, the sending and receipt of emails emits about 1.3 Mt of CO2e globally… every single day. As far as countries go, the 9.7 billion daily emails circulating among the ~306,000,000 users in the U.S. top the global list by emitting 3,207 tons of CO2e daily, while Irish email users emit the most per capita globally at 532.41 g daily (U.S. users average a much lower 9.2 g daily), and Indian email users the least, at only 2.07 g daily. A few weird numbers in the data suggest some serious spamming driving up per-capita numbers in places like Ireland and Austria, but you get the general drift.
Commenting on their study, a spokesperson for Zero Bounce noted the substantial carbon emissions of email demonstrate the need for greater awareness and strategies to reduce our personal digital carbon footprints. “Understanding the environmental impact of our digital communication practices is crucial for developing sustainable solutions and mitigating climate change,” they said.
Yet, it’s something few people think about when there’s actually—and obviously—plenty of evidence staring us in the face. Take hardware, the most tangible part of the equation. To produce smartphones, computers, monitors, printers, modems, routers and even cables requires massive inputs of electricity, raw materials that often include rare-earth metals, and all the extraction, manufacturing, transportation and distribution involved.
Environmental costs are further elevated due to how quickly electronic equipment wears out, finding itself languishing in landfill while we’re out buying the latest upgrades. Then there’s using the equipment—electricity needed to charge phones or laptops, to power routers and modems. Finally, there’s data transfer via LTE and 5G network transmitters or cable, and data centres whose servers process terabytes of data and consume huge amounts of electricity—more than 73 per cent of all emissions associated with the global digital carbon footprint, in fact, which is itself significant.
According to a 2020 Borderstep Institute publication, emissions from the production, use and disposal of digital technologies could be 1.8 to 3.2 per cent of global emissions from all sectors. And I haven’t even touched on the environmental impacts of social media. Topping the charts is TikTok (no surprise), which emits as much as 2.63g of CO2e per minute for each user; five minutes a day on this app contributes about 4,800g of CO2e per year per person, with the number of registered accounts now north of a billion; Instagram is in fourth place with 1.05g of CO2e per minute, and farther down the chart sits LinkedIn at 0.71g CO2e/min, X (formerly Twitter) at 0.60g CO2e/min and YouTube at 0.46g CO2e/min. This information has already had an impact on my scrolling behaviour and convinced me to delete some apps.
None of this should come as any surprise given the high profile of the emissions bomb associated with the data mining behind cryptocurrency. While this burgeoning financial sector provides opportunities and benefits, it also has major overlooked environmental impacts (doi.org/10.1029/2023EF003871). Bitcoin, the most popular cryptocurrency, was shown to be particularly concerning; a 400-per-cent increase in price from 2021 to 2022 triggered a 140-per-cent increase in energy consumption of the global Bitcoin mining network. China was the world’s top Bitcoin miner that year, followed by the U.S., Kazakhstan, Russia, Malaysia, Canada, Germany, Iran, Ireland and Singapore—collectively responsible for 92 to 94 per cent of the currency’s global carbon, water and land footprint.
Bitcoin mining emitted more than 85.89 Mt of CO2e during this period, with a shocking 67 per cent of the electricity required produced from a mix of fossil energy sources, dominated by coal at 45 per cent; the remaining sources were hydro at 16 per cent, nuclear at nine per cent, wind at five per cent, and solar at two per cent. Bitcoin’s annual emissions alone are sufficient to push global warming beyond the 2 C threshold, and would require planting 3.9 billion trees to offset—an area equivalent to the size of Switzerland or seven per cent of the Amazon rainforest.
In 2021–22, the global water footprint of Bitcoin mining was 1.65 km3, exceeding the domestic water use of more than 300 million people in rural sub-Saharan Africa. The land footprint of the global Bitcoin mining network was more than 1,870 square kilometres—1.4 times the area of Los Angeles. Countries like Kazakhstan, where electricity is heavily reliant on non-renewable energy but three times cheaper than in the U.S., provide major financial incentives for Bitcoin mining. Clearly and urgently, regulatory intervention and technological breakthroughs are needed to mitigate these environmental impacts.
And so, the digital world we have woven is indeed a tangled web when it comes to emissions and climate. But what of my email versus paper receipt quandary? Not to worry, it seems—the emissions from an email receipt are still more than 60-per-cent lower than those of the paper version. Whew!
Leslie Anthony is a biologist, writer and author of several popular books on environmental science.
