A new book might have you thinking twice before sending that pointless email.

The ground-breaking How Bad are Bananas?: The Carbon Footprint of Everything helped open the world’s eyes to people’s individual impact on the planet when it was first published back in 2009. Now it’s been updated to include a host of contemporary activities, from Twitter and Bitcoin to electric bikes and even space tourism.

Author Mike Berners-Lee is a carbon consultant who has forged a respected career advising firms and organisations on reducing their carbon footprints – long before many of us even knew what a carbon footprint was (here’s how to check yours). The new edition of the book includes often-surprising facts and figures on nearly 100 activities, all of which contribute to the average Brit’s annual footprint of around 13 tonnes.

Some of the worst offenders – flying, heating, cars – will be obvious, of course, but others might give you a little more pause for thought. Check out some of the more surprising figures below (spoiler alert: bananas aren’t actually that bad at all), and consider how making a few tweaks to your lifestyle could help address climate change.


It’s easy to assume that emails are green way to communicate, and compared to sending a letter they certainly are – but they still come with an environmental cost. According to Berners-Lee, sending the average email produces around 26g of carbon because of the electricity required to power equipment at each stage of the process: writing the email, powering the network that sends it, powering the data centre that stores it, and then the device it’s read on.

A Zoom call

There’s no doubt that teleconferencing has made our working lives easier (or more irritating, depending on who you ask), but like email, there’s a surprise footprint involved. Making a video call on a 13-inch MacBook Pro is responsible for about 2g of carbon per hour, but on a desktop computer with an external screen that shoots up to 50g per hour. Still, as Berners-Lee points out, this kind of technology has mitigated the need for face-to-face meetings, which in itself can save huge amounts of emissions, so the footprint involved in a Zoom call is relatively insignificant.

Electric bikes

This is where the number crunching gets really interesting. According to Berners-Lee, a mile on an electric bike is 20 times more carbon friendly than a mile on a push bike. How? Because in order to power a push bike you need to obtain energy from food. A mile by electric bike accounts for around 3g of carbon per mile, but a mile by push bike creates around 40g per mile if you’ve been ‘powered’ by bananas, 310g if you’re powered by cheeseburgers, or up to 4.7kg if you’re powered by air-freighted asparagus. However, electric bikes are far better than cars any day so definitely book a trial if you want to travel on two wheels. Here’s what you need to know.

A takeaway tea or coffee

In some cases, the biggest offender here is the disposable cup the drink is served in (110g of carbon), plus any milk. A black tea, for example, accounts for 22g of carbon. Add cow’s milk and that increases to 71g. Like a large latte? Choosing oat milk will give your beverage a footprint of 288g (not including the cup) – choose cow’s milk instead and that jumps to 552g. So a flat white is far better than a latte.


Despite the title of the book, it turns out that bananas are not a serious cause for concern when it comes to the emissions they’re responsible for, which is about 110g each. As Berners-Lee writes: “There are three main reasons bananas have such low carbon footprints compared with the nourishment they provide: they are grown in natural sunlight with no hot-housing; they keep well, so although they are often grown thousands of miles from the end consumer, they are transported by boats (about 1% as bad as flying); and there is hardly any packaging, because they have their own.”

The bottom line

Everyone has a carbon footprint – it’s an inevitable part of existence. But as How Bad are Bananas?: The Carbon Footprint of Everything shows, some activities are worse for the planet than others. Make a date with the updated version and get some inspiration for minimising your impact on the planet – and as a bonus you’ll definitely learn some interesting facts to impress your friends with!

How Bad Are Bananas?: The Carbon Footprint of Everything by Mike Berners-Lee, is published by Profile Books, priced £9.99.

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