Why do carbon dioxide emissions weigh more than the original fuel?

The amount of carbon dioxide (CO₂) that is produced from burning a fuel weighs more than the amount of the fuel itself, because during complete combustion, each carbon atom in the fuel combines with two oxygen atoms in the air to make CO₂. The addition of two oxygen atoms to each carbon atom forms CO₂, which has an atomic weight of 44—about 3.6667 times the atomic weight of the carbon, which is 12.

For example, subbituminous coal is, on average, 51% carbon, so the carbon in a short ton (2,000 pounds) of subbituminous coal weighs 1,020 pounds. The CO₂ emissions from burning a short ton of subbituminous coal weigh approximately 3,740 pounds, or about 3.67 times the weight of the carbon in a short ton of subbituminous coal and 1.87 times the weight of a short ton of subbituminous coal.

Learn more:
The periodic table of elements shows the atomic weights of all elements.
How much carbon dioxide is produced when different fuels are burned?

Last reviewed: February 1, 2023

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