Carbon emissions in our daily lives: what are they and how do they compare?

Do you know how much greenhouse gases were pumped into the air to produce your phone? And how much gases were emitted to grow the food we eat everyday? What about driving, flying, doing an internet search or using a computer? How much emissions do those daily actions generate?

If you ever wondered, as I often did, how big or small are the carbon emissions generated by the various things we do and the objects we use in our day-to-day living, the best place to start is Mike Berners-Lee’s book How bad are bananas? The carbon footprint of everything. Mike Berners-Lee is a professor and researcher at Lancaster University. (In case you wondered, he is the brother of world wide web inventor Tim Berners-Lee). The estimates in this article mainly come from his book, which helps answer questions such as: 

• How do carbon emissions compare?
• What are the orders of magnitude?
• How do emissions aggregate from small items to big ones?

First, what are we measuring?

First of all, you will ask, what is 1kg of CO₂? Take a balloon, and pump into it 559 liters of carbon dioxide gas, which is roughly half a cubic meter, approximately the volume of the trunk of a large car. Assuming the air temperature that day is 27°C, the balloon will then weigh 1 kg. Put differently, you will have trapped into it 1 kg of CO₂ gas (calculations by Philip D. Weyman, University of Missouri-St.Louis).

Numbers below are expressed in “carbon dioxide equivalent”, abbreviated as CO₂e. The reason for this is that there are different types of greenhouse gases, with different global warming potential. Using CO₂e makes it easy to compare greenhouse gas emissions. Over a period of 100 year, methane, for instance, causes 28 times as much warming than carbon dioxide in equal amount. Nitrous dioxide causes 265 times as much warming (estimations from the IPCC Fifth Assessment Report, 2014).

It is therefore convenient to use one single number to quantify all emissions generated by an object, instead of juggling with several ones.  In short, carbon dioxide equivalent is a measure of how much greenhouse gases are released into the atmosphere by an object or an action, counted as if only carbon dioxide was emitted, but in a quantity that would have the same global warming effect as would all other greenhouse gases involved in the process.

What are the emissions of small daily actions?

Now that we have an idea of what is 1kg of CO₂e represents, and knowing what the CO₂e unit is, here is a list of how many greenhouse gas emissions we produce in small daily actions (source unless mentioned otherwise: Mike Berners-Lee’s book How bad are bananas?).¹ To start with, how many emissions were generated to grow and transport the apple that I ate this morning?

• An apple: 10 g CO₂e if grown locally, up to 150 g CO₂e if shipped;
• A banana: 80 g CO₂e on average, including their transport (usually by boat); 
• Doing one search on a web search engine : 0.7 g CO₂e (low estimate, assuming an efficient laptop and power network) and up to 4.5 g CO₂e (half the emissions of an apple). Google estimates that each search on their engine generates 0.2 g CO₂e at their end. This is only one part of the total. The rest comes from the power consumed by the computer on our end, and the network in between.
• Sending or receiving an email: 4 g CO₂e for a normal email, 0.3 g CO₂e for a spam email, up to 50g CO₂e for an email with a long attachment. Besides, keeping an email in your mailbox generates about 10g CO₂e per year of storage, so the emissions of one apple. When you multiply by the number of emails stored and the number of years, this represents many apples!
• Watching TV for an hour: 34 g CO₂e on a small flat screen, up to 220 g CO₂e on a large plasma screen. This is the same as, for each hour of watching, the emissions of growing and shipping three apples, at the low end, and close to three bananas at the high end of the range.
• Watching Netflix for an hour or another video streaming service on your laptop: from 40 g CO₂e, in medium resolution, up to 270 g CO₂e in very high resolution (own calculations using measures on transmission data together with the “1byte” model developed by the think tank The Shift Project , see footnote for more details).²
• A box of 6 eggs bought at the shop: 1.8 kg CO₂e, roughly the emissions of four bananas for each egg.
• Washing the laundry: from 0.6 kg CO₂e if washed at 30°C and dried on the line, to 3.3 kg CO₂e if washed at 60°C and dried in a combined washer-drier.  
• Emissions of a hamburger: 2.5 kg CO₂e (standard hamburger with cheese and beef), 1 kg CO₂e for a vegan burger.
• A six-pack of beer: roughly 3.2 kg CO₂e according to this analysis prepared for a Belgian brewing company, which is around 0.5 kg CO₂e for each can of beer.
• Driving 1 km: from around 100 g CO₂e for a small efficient car recently built (in other words, one banana and one apple), and up to 500 g CO₂e for an old SUV (source: Carbon Footprint Calculator), roughly the emissions of growing six bananas, for each and every kilometer. Assuming you live 20 km away from your work, that your car is not old but not very recent either and that it emits around 200 g CO₂e per kilometer, you will end up with a commute generating 8 kg CO₂e every working day.
• A pair of shoes: 11.5 kg CO₂e on average (with most of the emissions generated during the production of the shoes, the rest during transport).

Emissions of bigger items: phones, computers, long-distance travel,…

Going up the emissions ladder, how much carbon do we pump into the air when we drive a car over a long distance or when we take the plane? Take a smartphone or a computer: how much carbon and other greenhouse gas are emitted to extract the raw materials used in each component, to transform and assemble the pieces, and to ship them as end products to warehouses and retail stores around the world? Again numbers below come from Mike Berners-Lee’s book How bad are bananas? unless mentioned otherwise:

• Phone: an old iPhone emits around 50 kg CO₂e into the atmosphere over its lifecycle, according to data from the producer, with about two thirds of those emissions to produce the phone, assuming the remaining third will be emitted during its use. The total emissions of the phone depends nevertheless very much on how often and how long we use it, Mike Berners-Lee stresses. On average, he argues, a smart phone will emit 47 kg CO₂e per year if used under 2 minutes per day. But the emissions will go up to 1.25 ton CO₂e per year if you use it one hour per day! The largest part of this footprint will be the electricity used to transmit your calls across the network.   
• Computer: the emissions released during the production of a computer range from 200 kg CO₂e, for a cheap, small unsophisticated laptop, to as much as 800 kg CO₂e for a big powerful desktop. You also need to add the electricity consumption for every hour of using the computer: 12 g CO₂e for a small laptop, up to 150 g CO₂e per hour for a big desktop. You  need to account as well for the emissions generated by your use of the Internet (servers and networks), estimated at around 50 g CO₂e per hour.
• Travel by plane: flying 1 km emits on average around 100 g CO₂e per passenger (slightly less in economy class, slightly more in business class). Producing emissions at high altitude, as commercial airplanes do, has an additional greenhouse effect linked to the emissions of nitrous oxides and water vapor. If we factor in this extra effect, the impact of flying roughly doubles with 200 g CO₂e per passenger per kilometer (source: UK government –  Greenhouse gas reporting: conversion factors 2019). A round trip from Cracow to, say, Malta, (1 100 km) will therefore emit around 250 kg CO₂e per passenger in economy class, and as much as 500 kg when accounting for the additional impact of flying at high altitude. Overall, this is an amount of emissions comparable with the production of a computer.  A round trip Paris-New York (5 800 km) in economy class will generate about 1 ton CO₂e per person on average, 2 tons if including the additional impact of flying at high altitude.
• Travel by car over long-distance: travelling by car will be slightly better than plane in terms of greenhouse gases, especially if more than one person sits in the car. Assuming your car is a few years old and emits around 200 g CO₂e per kilometer, a round-trip from Prague to Rome (1 300 km) will generate 260 kg CO2e. If you are two in the car, or more, this will already be better than flying.
• A carpet: assuming the size of the carpet is 4 m x 4 m, as in the example provided by Mike Berners-Lee, then the carbon bill to produce and transport it will range from 76 kg CO₂e for a thin polyurethane carpet, to close to 300 kg CO₂e for a thick luxury one.
• A mortgage: Mike Berners-Lee estimates that a mortgage of £100 000 on 5 per cent interest will generate 800 kg CO₂e per year! The reasoning behind this number is that running a bank, with all its building, offices and employee travel, emits significant amounts of greenhouse gases (as running any other company). Those emissions can therefore be split and allocated to the activities of the bank, in this particular case lending to private individuals, making it possible to calculate the average emissions generated by, in our example, one mortgage.
• A new car: the production of a car will generate around 6 ton CO₂e for a small model, up to 35 ton CO₂e for a big SUV. These greenhouse gases are emitted on your behalf if you purchase and become the owner of the car. If you resell the car a few years later, only part of the greenhouse gases emitted during its production enter your carbon balance, proportionate to the number of kilometers you drove in the car, over the total number of kilometers that the car will travel in its lifetime. In terms of greenhouse emissions, the longer the car will be used, the better. (Note that we are talking here only about the emissions generated during the production of the car, which are distinct from the emissions caused by the burning of gasoline in the engine, already discussed above).  

From individual emissions to world emissions

You can find many more examples of how carbon intensive our lifestyles can be in Mike Berners-Lee’s book How bad are bananas? The list above only gives an idea of the orders of magnitude to help understand and compare greenhouse gas emissions associated with a number of everyday activities.

When we add up all these emissions and a few more, we reach a total of roughly 7 ton CO₂e emitted on average per person per year. (This is a world average using 2019 figures, see next post for the details of the calculation). To get a sense a what this figure means, 7 ton CO₂e is as much greenhouse gas as:

• 7 trips by plane from Paris to New York, and back;
• driving 35 000 km (with the same assumption that your car is a few years old and emits around 200 g CO₂e per kilometer);
• producing a relatively small car;
• manufacturing 35 small laptop computers, or close to nine big powerful desktop computers;
• producing about 600 pairs of shoes;
• or, finally, growing and shipping about 87 000 bananas!

In light of the numbers presented above, and following the lead of Mike Berners-Lee, I confess my unstated goal in writing this post was to make the case for the importance of learning carbon literacy skills in an age of global heating. In one of the best review I found of Mike Berners-Lee’s book, (“Uncovering the Carbon Footprint of Everything,” Our World portal, United Nations University), the author, Alva Lim, sums it all up by inviting us to:

“recognise, à la Newton, that for every action there is an equal and opposite (greenhouse gas) reaction.”

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1 Unless stated otherwise, numbers in this article come from Mike Berners-Lee’s book How bad are bananas? The carbon footprint of everything, Profile Books (2010 edition). For the emissions of an apple, see page 26, a banana: page 27, a web search: page 12, an email: page 15, an hour of TV: page 30, a box of eggs: page 69, a load of laundry: page 84, a hamburger: page 86, a pair of shoes: page 105, a mobile phone: page 113, a computer: page 134, travel by car: page 65, a carpet: page 112, a mortgage: page 127,  a new car: page 143. December 2020 update: Mike Berners-Lee published a new version of the book in September 2020 (Profile Books), with new sections and updated figures (the aforementioned URL links directly to the second edition).

2 The Shift Project developed the “1byte” model to estimate the energy impact of transmitting data across the network. This impact, multiplied by a carbon intensity factor (for simplicity I used here the world average factor), gives an estimation of the amount of greenhouse gas emissions generated by the electricity used for the transmission of data across the network. The model was presented by The Shift Project in its report “Lean ICT: Towards Digital Sobriety” (March 2019, Excel file with the model available here). Figures on data traffic come from the article “How Much Data Does Netflix Use?”, by Cameron Summerson on How-To Geek (January 2018). It is worth mentioning a subsequent study published by The Shift Project: Climate crisis: The unsustainable use of online video – A practical case study for digital sobriety (July 2019), as well as a Firefox browser extension developed by The Shift Project, Carbonalyser, which calculates the greenhouse emissions associated with our internet navigation.