Beth Kayser

What is a carbon footprint?

3 min Read
Aerial view of a carrot lying next to a measuring tape against a blue background

An individual, a business, a community, even the device you’re using to read this paragraph will have a carbon footprint.

The dictionary defines a carbon footprint as the amount of carbon someone/thing produces, but that’s out of date. These days when someone uses the term, they’re referring to the impact that a person, object or entity has on the environment in terms of GHG.

“Carbon footprint” is a catchall term for the amount of greenhouse gas (GHG) something or someone is responsible for.

GHG includes carbon dioxide, methane, nitrous oxide, and fluorinated gases but for simplicity we bucket them all together and express them as an amount of carbon dioxide equivalent; or ‘CO2e’.

How do you measure a carbon footprint?

There are many different standards and approaches to carbon footprinting, which is why you’ll see a variety of numbers circulating for the same thing. For example, some put the average UK carbon footprint at 5.6 tonnes CO2e per year, we (Pawprint) put it at 12.7 tonnes.

Why is ours so much higher? Well, taking the lead from our carbon expert Mike Berners-Lee (author of How Bad are Bananas? The Carbon Footprint of Everything) and his team at Small World Consulting, we believe a carbon footprint must account not only for direct emissions but also for indirect emissions.

It’s easier to use an example to explain what we mean by that, so let’s look at your smartphone. It holds:

  • Embodied CO2e: the CO2e produced when making a product. In your smartphone’s world, that’s the emissions from design, resource extraction, manufacturing and from transporting it from the factory to your front door. According to Mike, you’re looking at about 105kg CO2e just to make your phone (based on the iPhone 11 128GB).
  • Use-phase CO2e: this comes from the energy your phone uses while it’s charging and its portion of internet emissions. Here you’re looking at about 69kg CO2e per year (or 1g per minute), based on 3 hours per day.
  • End of life CO2e: the average person keeps a phone for two years (Journal of Cleaner Production, 2018), then it ends up in a drawer for ages, gets handed down to a younger sibling or gets sold on. Eventually, however, the phone either ends up in recycling or on the landfill heap; or a bit of both. E-waste is a growing problem for many reasons including damage/disturbance to biodiversity and leakage of harmful substances into the soil and air. Even recycling uses energy which, of course, means more emissions (although these should be offset by the energy saved from reusing something that already exists instead of creating something from scratch).
Pie chart showing the carbon footprint an iPhone 11 used for one year, based on 3 hours per day. Internet 22%, electricity 1%, embodied 77%
Carbon footprint of a year's usage of an iPhone 11, based on 3 hours per day. Use-phase accounts for 23% of emissions; embodied carbon 77%.

In this example, the smartphone manufacturer would know to count direct emissions from design, manufacturing and transport because they all result from internal activity, but might not consider indirect emissions from resource extraction, repairs, data centres, waste, etc.

To quote Mike from his book, ‘[t]racing back all the things that have to happen to make that [phone] leads to an infinite (and I am using that word carefully) number of pathways, many of them tiny but important when they are all added together.’

In short, when you include direct and indirect emissions in a carbon footprint, it gets hard… really hard. But ignoring them isn’t the answer, because that tends to lead to massive underestimations in the carbon numbers.

So what is the answer? Well, this is another little golden nugget we’ve stolen from Mike; the ‘good enough’ philosophy. No carbon footprinting is 100% accurate, and spending loads of time trying to get it perfect can (in some instances) actually be a bad use of time. Instead, we focus on getting the numbers ‘good enough’ to get the orders of magnitude right. For example, understanding that beef is 3 times worse than chicken is enough for you to know which one to choose if you’re trying to lower your carbon footprint. The fact that it’s 10kg CO2e out won’t prevent you from making the right decision.

What’s more, we may be 10kg out but that’s because we’ve tried to look at the entire picture. We’d rather do this than only look into what’s easy and be spot on, even if it does mean that a tiny piece of Shauna’s perfectionism dies each time she does it.  

At Pawprint, we see it as our job to help you make the right choices with the information that’s available. Because we don’t have time to stall on the climate crisis; it’s now or never.

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SMART has a useful interactive wheel if you’d like to learn more about the lifecycle of a phone

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