Measuring footprints

Measuring Ecological Footprints

Ecological footprints look at human activities and the natural resources they require. The amount of a particular product that a person consumes can be related back to the area of land or sea that was needed to produce it or dispose of the waste.

Ecological footprint of a car

Carbon dioxide is produced by petrol engines. This can be taken in by plants. But what area of plants are needed to take in the carbon dioxide produced by a car?

A typical medium-sized car produces 160g of CO₂ per km.

Driving 10,000km per year would produce a total of 1.6 tonnes of CO₂.

A conifer forest takes in 3 tonnes of CO₂ per hectare per year as they grow using photosynthesis.

To remove 1.6 tonnes of CO₂ requires 0.53 hectares of forest (^1.6/₃).

So, just over half a hectare of forest will remove the carbon dioxide produced by one car in a year. That is an area of forest about the size of a football pitch. That is the car's ecological footprint.

Electric-petrol hybrid cars are now being sold that are more efficient. These will have a smaller ecological footprint than conventional petrol cars.

Of course, this footprint does not include resources used in the car's production or disposal.