It seems impossible that a gallon of gasoline, which weighs about 6.3 pounds, could produce 20 pounds of carbon dioxide (CO 2 ) when burned. However, most of the weight of the CO 2 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 (H 2 O), and carbon combines with oxygen to form carbon dioxide (CO 2 ).

A carbon atom has a weight of 12, and each oxygen atom has a weight of 16, giving each single molecule of CO 2 an atomic weight of 44 (12 from carbon and 32 from oxygen).

Therefore, to calculate the amount of CO 2 produced from a gallon of gasoline, the weight of the carbon in the gasoline is multiplied by 44/12 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).