One US Gallon of Gasoline Produces 20 Pounds of Carbon Dioxide (CO2)

Scientists keep telling me that when I drive my car, I have a huge carbon footprint from the green house gases ( C02) that are produced, but I raelly have no sense of how bad I really am. According to the US Department of Energy, one US gallon of gasoline produces 20 pounds of carbon dioxide.

"It seems impossible that a gallon of gasoline, which weighs about 6.3 pounds, could produce 20 pounds of carbon dioxide (CO₂) when burned. However, most of the weight of the CO₂ doesn't come from the gasoline itself, but the oxygen in the air.

When gasoline 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 carbon atom has a weight of 12, and each oxygen atom has a weight of 16, giving each single molecule of CO₂ an atomic weight of 44 (12 from carbon and 32 from oxygen).

Therefore, to calculate the amount of CO₂ produced from a gallon of gasoline, the weight of the carbon in the gasoline is multiplied by 44 divided by 12 or 3.7.

Since gasoline is about 87% carbon and 13% hydrogen by weight, the carbon in a gallon of gasoline weighs 5.5 pounds (6.3 lbs. x .87).

We can then multiply the weight of the carbon (5.5 pounds) by 3.7, which equals 20 pounds of CO₂!

Molecular Weight of CO₂ by Constituent

Sources: www.fueleconomy.gov; Properties of Fuels (PDF 246 KB), U.S. Department of Energy (DOE), Alternative Fuels Data Center (AFDC).