1.2 The carbon footprint boundary

Depending on where you draw the boundary, the carbon footprint can apply to: an individual or household; an organisation, event or product; a city, region or country. In this course you will mainly be considering the footprints of individuals, households and the countries they inhabit.

But even then the boundary needs to be defined carefully. Sometimes the carbon footprint is taken to mean an individual’s or household’s direct CO₂ emissions, mainly from burning fossil fuels for home heating and car driving. But this leaves out their indirect CO₂ equivalent emissions arising from the production and distribution of the food, drink and other goods and services they consume, ranging from clothes and electronic products to banking, medical services and Open University modules.

Again depending on the boundary, these indirect emissions often include only those arising from the food, goods and services produced within the country where people live. But they may also include the emissions ‘embedded’ in imports; for example, the emissions produced by the ‘supply chain’ of mines, farms, factories, trucks and ships involved in making and transporting the food, cars and computers that Britain imports from the EU and China.

Whichever measure you choose, the ‘footprint’ image is used to suggest an individual or group treading on or occupying the Earth (Figure 2). It implies that the Earth can’t indefinitely support the lifestyle of that individual or group, and if they are to live sustainably, they’ll have to lighten their footprint.

(adapted from Berners-Lee et al., 2011).

Figure 2 The footprint as a powerful image of treading on or occupying the Earth. A UK individual’s carbon footprint arises mainly from home energy use and personal travel, including flights, and from consumption of food, goods and services.

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This figure is a sketch of a human footprint divided horizontally into five sections. The toe section represents the mass of carbon dioxide equivalent emissions arising from an average UK inhabitant’s purchase and use of UK produced and imported consumer goods and services, at about 4 tonnes CO2 equivalent per year. The ball of the foot section represents the mass of carbon dioxide equivalent emissions arising from an average UK inhabitant’s travel by car, air, public transport and bicycle, at about 3.5 tonnes per year. The upper arch of the foot section represents the mass of carbon dioxide emissions arising from an average UK inhabitant’s home energy use for heating, lighting, etc., at about 3 tonnes per year. The lower arch section represents the mass of carbon dioxide equivalent emissions arising from an average UK inhabitant’s consumption of food and drink, also about 3 tonnes per year. The heel section represents the mass of carbon dioxide equivalent emissions arising from an average UK inhabitant’s use of public and government services ranging from education and investment in roads to defence, at about 2.5 tonnes per year.

Figure 2 The footprint as a powerful image of treading on or occupying the Earth. A UK individual’s carbon footprint arises mainly from ...