Carbon footprints and how to cut them
What a footprint counts
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.
Methane and other gases are converted to the amount of carbon dioxide with the same warming effect.
Ways to reduce it:
- Use renewable energy (solar, wind) or nuclear power instead of fossil fuels.
- Use less energy: insulation, efficient lighting and heating, turning things off.
- Carbon capture and storage: catch carbon dioxide at power stations and store it underground.
- Carbon taxes and licences make high-emission choices cost more.
- Plant trees, travel less, and reuse and recycle.
Why it is hard: new technology costs money, countries do not always agree, and people may not want to change their lifestyle.
Working out a footprint
- A home uses 3000 kWh of electricity a year at 0.25 kg of carbon dioxide per kWh
- footprint = 3000 × 0.25 = 750 kg = 0.750 tonnes
- LEDs save 400 kWh: 3000 − 400 = 2600 kWh; solar then supplies 25%, so 2600 × 0.75 = 1950 kWh from the grid
- new footprint = 1950 × 0.25 = 487.5 kg = 0.488 tonnes (3 s.f.)
For a shared car journey, divide the car's emissions between the people in it before you compare with a train.
- (Higher) Burning 32 kg of methane: CH₄ + 2O₂ → CO₂ + 2H₂O
- Mr: CH₄ = 16, CO₂ = 44; 16 kg of methane gives 44 kg of carbon dioxide
- mass of carbon dioxide = 32 × 44 ÷ 16 = 88 kg
Check which way round the ratio goes: a fuel gives a larger mass of carbon dioxide than its own mass, because oxygen from the air is added.
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