a common reader

The carbon footprint of everything

· 4 August 2014 |  by Maarten
· Published in: FOCUS · wetenschap
· Tagged with:

Mike Berners-Lee, How Bad Are Bananas?Mike Berners-Lee
How Bad Are Bananas?

Berners-Lee starts off this terrifically interesting book hoping that “I can take three things for granted:

  • climate change is a big deal;
  • it’s man-made
  • and we can do something about it.”

Those of us who do want to lower their own impact, should first of all acquire a carbon instinct, a good grasp of the kinds of numbers we’re talking about when we want to say something like “Eating meat causes ‘lots of’ greenhouse gas emissions.” This book is intended to help us build such an instinct: it’s filled with information about the greenhouse gas emissions associated with all kinds of things, from foodstuffs to books, emails, modes of transport, and more.

For each item, we get not only some numbers,1 but crucially also interpretations, comparisons, hidden assumptions. The results are always surprisingly interesting, and often challenged my preconceptions.

To give you a taste, here are some excerpts from the book (small ones: the book typically dedicates more than a page to each item).


A plastic carrier bag

3 g CO2e very lightweight variety
10 g CO2e standard disposable supermarket bag
50 g CO2e heavyweight, reusable variety

When someone in the developed world walks home from the shops with a disposable plastic bag full of food, the bag is typically responsible for about one-thousandth of the footprint of the food it contains. In other words, it is good if your supermarket is taking action on plastic bags, but don’t let that stop you from asking what it is doing about the other 999 thousandths of its carbon agenda.

A banana

80 g CO2e each, or 480 per kilo

To answer the question in the title of this book, bananas aren’t bad at all. They’re brilliant! To emphasize the point, I’m eating one as I write.

There are three main reasons that bananas have such low carbon footprints compared with the nourishment they provide:

  • They are grown in natural sunlight
  • They keep well, so although they are often grown thousands of miles from the end consumer, they are transported by boats (about 1 per cent as bad as flying2).
  • There is hardly any packaging, if any, because they provide their own.

A red rose

Zero g CO2e picked from your garden, no inorganic fertiliser used
350 g CO2e grown in Kenya and flown by air
2.1 kg CO2e grown in a heated greenhouse in the Netherlands

A single red rose could have the same impact on climate change as about four and a half kilos of bananas.

A pint3 of milk

723 g CO2e

Milk is high-carbon stuff for exactly the same reasons that beef is. Cows, like most animals, waste a lot of energy in the food they eat in the process of simply keeping warm and walking around rather than creating meat and milk. In addition, cows ruminate (chew the cud) which means they burp up methane, roughly doubling the footprint of the food they produce.

A paperback book

400 g CO2e recycled paper, with every copy printed getting sold
1 kg CO2e average
2 kg CO2e the same book on thick virgin paper, with half the copies getting pulped

The carbon footprint of a typical paperback is about the same as watching 12 hours of programmes on an average TV.

A pack of asparagus

125 g CO2e 250g pack, local and seasonal
3.5 kg CO2e the same pack, air-freighted from Peru to the UK in January

It is over 100 times more carbon-efficient to get your calories from bread [as from the air-freighted asparagus].

1 kg of rice

2.5 kg CO2e efficiently produced
4 kg CO2e average
6.1 kg CO2e inefficient production with excessive use of nitrogen fertiliser

A typical kilo of rice causes more emissions than burning a litre of diesel.

I suspect that plenty of greens will be slightly unsettled to hear that rice, the simplest of foods, is a surprisingly high-carbon staple, much more so than wheat, which is nutritionally similar. That’s because of the methane that bubbles out of the flooded paddy fields and the excessive helpings of fertiliser that are all too often applied.

1 kg of tomatoes

0.4 kg CO2e organic loose tomatoes, traditional variety, grown locally in July
9.1 kg CO2e average
50 kg CO2e organic ‘on the vine’ cherry tomatoes, grown in the UK in March

Shocking! Tomatoes, at their worst, are the highest-carbon food in this book. But at their best, tomatoes are perfectly fine.

1 kg of cheese

12 kg CO2e hard cheese

It takes about 10 litres of milk to make 1 kg of hard cheese, adding up to a considerable carbon footprint that’s higher than that of many meats. The message is clear, then: going veggie doesn’t reduce your impact if you simply swap meat for cheese.4

London to Glasgow and back

53 kg CO2e banana-powered bike
66 kg CO2e coach
120 kg CO2e train
330 kg CO2e small efficient car
500 kg CO2e plane
1100 kg CO2e large four-wheel drive

All these scenarios are based on one person travelling the 405 miles5 each way on their own.

The plane could actually be better than driving if you have the wrong kind of car. (My sums are based on flying economy class.) But please don’t take this as an advert for flying: it’s just a reminder of quite how carbon-profligate some road vehicles are.

A hectare of deforestation

500 tonnes CO2e

That’s equivalent to an average car driving 700,000 miles – 28 times around the world.

Halting deforestation is potentially one of the easiest climate-change wins. The Amazon Fund pays [Brazilian] farmers to hang on to their trees. It works out at just £3 per tonne of carbon saved. What a bargain! Why doesn’t the UK government get into this kind of thing instead of supporting photovoltaic panels at less than one-hundredth of the carbon benefit per pound invested?

A volcano

1 million tonnes CO2e Mount Etna in a quiet year
42 million tonnes CO2e Mount Pinatubo, Philippines, 1991

If you have been a victim of the rumour, persistent in some circles, that volcanic emissions dwarf those of human activity, now is the time to be liberated. All the world’s volcanoes together produce a total of about 300 million tonnes of CO2e per year. This is well under 1 per cent of the annual emissions from mankind’s activities.

The world’s data centres

130 million tonnes CO2e 2010
250–340 million tonnes CO2e prediction for 2020

Digital data as a whole is looking set to climb to well over 1 per cent of total emissions. Digital information may not be lower-carbon than the paper-based world of 20 years ago.

Of course, if we go for digital information without ditching the paper, downloading stuff simply to print it out, we end up with the worst of all carbon worlds.


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  1. The numbers are expressed in “CO2 equivalent”: a measure for the combined greenhouse impact of different amounts of various greenhouse gases: CO2, methane, nitrous oxide and others.
    To give some meaning to “1 kg CO2e”, Berners-Lee refers to “the 10-tonne lifestyle” as an achievable goal for the conscious person: the average UK person has an annual carbon footprint of around 15 tonnes.

  2. Elsewhere, the book says that road transport is, kilometer per kilometer, about as bad as flying. So freight goods coming 100 km by road have a similar impact as those coming 10,000 km by boat!

  3. About 0.47 litres.

  4. I should reconsider my diet choices now…

  5. 652 km



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