What’s in a tonne of carbon dioxide? — Nula Carbon

9 min readFeb 16, 2021

It seems we constantly keep hearing about carbon and how individuals, organisations, or governments are pledging to reduce their respective footprints.

This is usually denoted in the ‘tonnes of carbon’ or tCO2e (as the carbon dioxide equivalents) that are ‘reduced’, ‘emitted’ or ‘saved’.

Collectively we emit about 50 gigatonnes of CO2e each year, which is about 40% higher than we did just 30 years ago in 1990 [1]. This certainly sounds like a lot, however it can be difficult to get one’s head around just how much this actually is.

To get a perspective of what one tonne may look like, a company called Carbon Visuals created a neat video to highlight New York City’s emissions as one-tonne spheres of carbon dioxide:

Still though, it’s necessary to cut through the jargon and answer some crucial questions: what is carbon? And what does a tonne of it amount to?

What is ‘carbon’?

Carbon is the foundation of all things living on Earth and by itself it makes up about 0.0025% of the Earth’s crust [2]. It helps regulate our planet’s temperature and provides us with conditions fit to sustain ourselves through the growing of foods.

The atmosphere i.e. the layer around the Earth is made up of gases, where carbon dioxide is also present. By way of the carbon cycle, carbon travels between the Earth to the atmosphere (and other spheres!). Down on our planet it’s mostly stored in rocks, the ocean and in living organisms [3].

One tonne of carbon dioxide is often denoted as tCO2. When we want to take into account other greenhouse gases, we denote this as a tonne of carbon dioxide equivalent or tCO2e*.

While it can be viewed as reductionist to standardise complex science into pure tonnes of carbon dioxide equivalents, it can allow us to see the relative impact of our actions [4].

What’s in a tonne anyway? Travel and transport

While travel and use of transport is seemingly rather limited at the moment, it’s still worthwhile to consider that not all produce the same effect. For instance:

A combination of our lifestyle choices and where we live influence the extent of our environmental footprint. As an example, one tonne of carbon dioxide equivalent amounts to:

Around one month’s emissions from an average person in the U.K (where per capita emissions are 12.1tCO2e per year [9].
In comparison, one tonne amounts to more than a year of emissions for an average person living in Sri Lanka!

Of course there are major structural and developmental differences between the above comparison. However, efforts should prioritise minimising excess and living within a planetary boundaries, which are clearly outstretched.

Source: The EU-28 (pre-Brexit) showing planetary boundaries among different social and ecological indicators.

Good Life For All Within Planetary Boundaries, University of Leeds, 2021 .

Our daily habits also have a varying degree of impact depending on how we live. For instance:

We’ve highlighted the considerable effect that switching up one’s diet has on our own footprint (see: ). So what does this look like in terms of a tonne?

Eating beef 4 meals a week for one year would result in approximately a tonne of carbon emissions [8].
However, by switching this out to seafood it would take you 5 to 12 times longer to emit the same amount of carbon** [11].

By taking these comparisons into account we can start to realise the impact that our lifestyles have on our environmental footprint. It’s important that individuals, organisations, and governments all practice environmental accountability and it starts with knowing what we are emitting in the first place.

Sources:

[1] Greenhouse gas emissions by Hannah Ritchie and Max Roser, 2021.

[2] by Encyclopaedia Britannica.

[3] What is the carbon cycle? by NOAA, 2020

[4] One Tonne of Carbon Dioxide Equivalent (1tCO2e) by Julia Dehm, 2018.

[5] ClimateCare Carbon Calculator by ClimateCare, 2021.

[6] Environment by Eurostar, 2021.

[7] The climate mitigation gap: education and government recommendations miss the most effective individual actions , by Seth Wynes and Kimberly Nicholas, 2017.

[8] Greenhouse gas reporting: conversion factors 2020 , by UK Government, 2020.

[9] A Good Life For All Within Planetary Boundaries, Country Comparisons by the University of Leeds, 2021.

[10] Carbon Literacy Guide by Scottish Government, 2018.

[11] You want to reduce the carbon footprint of your food? Focus on what you eat, not whether your food is local by Hannah Ritchie, 2020.

Notes:

* Carbon dioxide equivalents — CO2e:

To capture all GHG emissions, including carbon dioxide, methane, nitrous oxide, and other gases, researchers use the term “carbon dioxide-equivalent” or CO2e.
To express this, each greenhouse gas is weighted in terms of their Global Warming Potential or GWP. This measures the warming impact of one unit mass of a greenhouse gas relative to carbon dioxide over a given timescale (usually 100 years).
For example, one tonne of methane has a GWP of 28 meaning it creates 28 times higher warming impact than one tonne of carbon dioxide over a 100-year period.

** takes into account a range of seafood options such as fish (farmed) and prawns (farmed) (Source: Ritchie, 2020 )

Ilkka is a sustainability consultant, content creator, and carbon researcher currently residing in Edinburgh. He became passionate about the environment through seeing wasteful practices working as a chef in commercial kitchens and through spending time living in Malaysia. As a result, he studied an MSc in Carbon Management at the University of Edinburgh and aspires to continue making a difference through his work. You can follow his content journey through Instagram over at: and his .