Calculation of CO₂ emissions

The amount of carbon dioxide a vehicle emits into the air is directly proportional to the amount of fuel it uses and the carbon content of the fuel.

Exhaust emissions, in particular carbon dioxide emissions, are one of the major issues of the day. Although it is quite a controversial and wide-ranging topic, the basic calculation of the amount of CO₂ emitted by a vehicle is fairly straightforward. It all depends on fuel consumption and the amount of carbon contained in the fuel type.

Carbon dioxide (CO₂) emissions are given in grams per kilometre travelled, all calculated from the combined consumption determined by the WLTP measurement cycle. A simplified calculation might read:

*fuel type*	*the amount of carbon dioxide produced by burning 1 litre of fuel [g]*
diesel	2640
petrol	2390
LPG	1660
CNG	2666

A full description of the calculation methodology can be found, for example, on the website of the US Environmental Protection Agency – EPA.

Calculation of CO₂ emissions for a diesel engine:

1 litre of diesel weighs 835 grams and contains 86.2% carbon, which is equivalent to 720 grams of carbon in each litre of diesel. It takes 1920 grams of oxygen to burn 1 liter of diesel. The carbon dioxide produced is therefore equal to the sum of 720 grams of carbon and 1920 grams of oxygen. That’s 2640 grams of CO₂ per litre of diesel burned.

Example:
with an average consumption of 5 litres per 100 km, the CO₂ emissions5/100 x 2640 = 132 grams of CO₂per travelled kilometre

Calculation of CO₂ emissions for a petrol engine:
1 litre of petrol weighs 750 grams, contains 87% carbon, which is equivalent to 652 grams of carbon in each litre of petrol. It takes 1740 grams of oxygen to burn 1 litre of petrol. The carbon dioxide produced is therefore equal to the sum of 652 grams of carbon and 1740 grams of oxygen. That’s 2,392 grams of CO₂ from one litre of gasoline burned.

Example:
with an average consumption of 5 litres per 100 km, the CO₂ emissions5 x 2392 / 100 = 120 grams of CO₂per travelled kilometre

Calculation of CO₂ emissions for LPG fuel:
1 litre of LPG weighs 550 grams, contains 82.5% carbon, which corresponds to 454 grams of carbon in each litre of LPG. It takes 1211 grams of oxygen to burn 1 litre of LPG. The carbon dioxide produced is therefore equal to the sum of 454 grams of carbon and 1211 grams of oxygen. That is 1665 grams of CO₂ from one litre of LPG burnt.

Example:
with an average consumption of 5 litres per 100 km, the CO₂ emissions5/100 x 1665 = 83 grams of CO₂per travelled kilometre

Calculation of CO2 emissions for CNG drive in the High variant:

1 kilogram of CNG contains 72.7% carbon, which corresponds to 727 grams of carbon in each kilogram of CNG. It takes 1939 grams of oxygen to burn 1 kilogram of CNG. The carbon dioxide produced is therefore equal to the sum of 727 grams of carbon and 1939 grams of oxygen. That’s 2666 grams of CO₂ from one kilogram of CNG burned.

Example:
with an average consumption of 4 kilograms per 100 km, the CO₂ emissions4/100 x 2666 = 106,6 grams of CO₂per travelled kilometre