The carbon footprint and its reduction: The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane.

The idea

Reducing a carbon footprint means cutting the amount of carbon dioxide and methane released at every stage of a life cycle. Carbon dioxide comes mainly from burning fossil fuels for electricity, heating and transport, so using renewable energy, insulating buildings and travelling less by petrol or diesel car all help. Methane comes from livestock, landfill sites and leaks from natural gas extraction and distribution, so eating less meat, capturing landfill gas and fixing leaks reduce it. Because methane traps much more heat per molecule than carbon dioxide over short timescales, cutting methane can give a quick reduction in warming even though the mass released is smaller. A useful method is to identify the largest emission stage, target it first, then re-measure the total to check the reduction.

What earns the marks

• States that reducing carbon dioxide emissions lowers the carbon footprint, with a valid example such as using renewable electricity.
• States that reducing methane emissions lowers the carbon footprint, with a valid example such as capturing landfill gas or reducing livestock numbers.
• Explains that methane is a more potent greenhouse gas than carbon dioxide over short timescales, so cutting it has a strong effect.
• Applies the idea to a specific life-cycle stage, such as transport, electricity generation or waste disposal.
• Recognises that reductions must be measured across the whole life cycle, not just at one stage.

Common mistakes and how to put them right

• Claiming that only carbon dioxide matters.

  Put it right by explaining that methane is also a greenhouse gas and must be reduced.

• Suggesting that recycling alone removes a carbon footprint.

  Put it right by stating that recycling reduces some emissions but other stages still release greenhouse gases.

• Confusing methane with carbon dioxide sources.

  Put it right by linking methane to livestock, landfill and gas leaks, and carbon dioxide to fossil fuel burning.

Exam tips

• Name the gas and the source together, for example methane from landfill, to make the reduction method clear.
• Use comparative language such as more potent or greater warming effect when discussing methane.
• Link each reduction method to a named life-cycle stage so the answer stays specific.