# CO 2 emissions

How can using 1 litre of gasoline emit 2.4 Kg. of CO2? This is what my AirCare result sheet tells me - AirCare being the mandatory emissions test that all passenger cars have to go through before insuring in BC.

Over 2/3rds of the mass comes from the oxygen, which comes from the air.

Some quick googling yields about 0.75g/ml as gasoline’s density, or about 750 grams for a liter. However, remember that burning gasoline is a combustion process; chemically, burning is an oxidation reaction. This turns gasoline (a mixture of carbon and hydrogen with a few trace contaminants and additives) into combustion byproducts, generally CO, CO2, and H2O. All those extra oxygens come from the atmosphere and contribute to the mass of the emissions.

As oxygen is slightly heavier than carbon (with atomic masses 16 and 12, respectively,) your statistic doesn’t seem unreasonable.

Ballparkin it:
About 80% of the mass of gasoline is in the form of carbon.
1 liter masses about 750 grams, so that’s about 600 grams of carbon.
It’ll take about 1600 grams of oxygen to convert that to carbon dioxide.
1600 + 600 = 2.2 kg.

So that 2.4 kg number is about right.

Thanks. I just didn’t think that combustion would add so much mass/weight. Makes sense now.