The Carbon Footprint

This lesson covers the concept of the carbon footprint and how it can be reduced, as required by AQA GCSE Chemistry specification (5.9.2). You need to understand what a carbon footprint is, how it is measured, the actions that individuals, businesses, and governments can take to reduce it, and the challenges involved in doing so.

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What Is a Carbon Footprint?

A carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service, or event. It is usually expressed in units of tonnes of carbon dioxide equivalent (tCO₂e) per year.

The "carbon dioxide equivalent" (CO₂e) is used because different greenhouse gases have different global warming potentials. For example, one tonne of methane has the same warming effect as approximately 25 tonnes of carbon dioxide over 100 years, so it is counted as 25 tCO₂e.

Exam Tip: The definition of carbon footprint must include "other greenhouse gases" — not just carbon dioxide. The AQA specification explicitly states it is the total amount of CO₂ AND other greenhouse gases. Leaving out "other greenhouse gases" will lose you the mark.

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Measuring Carbon Footprints