Carbon dioxide: a leading greenhouse gas

Carbon dioxide (CO2) is emitted from cars after the burning of fossil fuels such as petrol, diesel or even natural gas/LPG. It is one of five main emissions from petrol and diesel cars. The others are carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons and particulates.

Although CO2 emissions are not directly harmful to us, they are recognised as a leading greenhouse gas, causing global warming. CO2 emissions from cars are directly proportional to fuel consumption, and as diesel cars use less fuel, they emit less carbon dioxide than petrol cars.

While natural gas and LPG cars emit less CO2 than petrol or diesel, they are less fuel-efficient so the net CO2 result over a journey can often be worse.

Hybrid cars such as the Toyota Prius match a petrol engine with batteries which recharge during braking. Due to less use of the petrol engine these vehicles use less fuel and therefore emit less CO2 than would be normal for a regular car. Some car firms are working towards the introduction of viable plug-in electric cars, but while these will not emit CO2 directly, the creation of electricity through the burning of coal, peat or oil at powerstations still creates CO2 emissions.