Category: Features      How can a litre of petrol produce 2.3kg carbon dioxide?...

## How is that Possible?

It seems impossible that a litre of petrol, which weighs about 0.73 kg, could produce 2.3 kg of carbon dioxide (CO2) when burned. However, most of the weight of the CO2 doesn't come from the petrol itself, but the oxygen in the air. When petrol burns, the carbon and hydrogen separate.

The hydrogen combines with oxygen to form water (H2O), and carbon combines with oxygen to form carbon dioxide (CO2).
A fuel (CO2) carbon atom has a weight of 12, and each oxygen atom has a weight of 16, giving each single molecule of CO2an atomic weight of 44 (12 from carbon and 32 from oxygen).

Therefore, to calculate the amount of CO2produced from a litre of petrol, the weight of the carbon in the petrol is multiplied by 44/12 or 3.7. Since petrol is about 87% carbon and 13% hydrogen by weight, the carbon in a litre of petrol weighs 0.63 kg. We can then multiply the weight of the carbon by 3.7, which equals 2.3 kg of CO2.

1 litre of diesel typically weighs 0.83kg (the density range is 820-845kg/m3 in Europe and up to 860kg/m3 elsewhere). About 87% of this is carbon, so one litre of diesel contains 0.83 x 87% = 0.722kg of carbon, each atom of carbon weighs 12 atomic units. When it combines with two atoms of oxygen in the combustion process it becomes CO2, which weighs 44 atomic units.

The 0.722kg of carbon in the original fuel then becomes 0.722 x 44/12 = 2.65kg of CO2, so one litre of diesel fuel produces about 2.65kg of CO2  