The vehicles we drive release over 1.7 billion metric tons of greenhouse gases (GHGs) into the atmosphere each year—mostly in the form of carbon dioxide (CO2)—contributing to global climate change. Each gallon of gasoline you burn creates 20 pounds of CO2. That’s about 6 to 9 tons of CO2 each year for a typical vehicle.
How can 6 pounds of gasoline create 19 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 CO2doesn’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 44/12 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!
Physical and chemical properties of gasoline: Department of Energy (DOE), Alternative Fuels Data Center (AFDC), Properties of Fuels.
What Can I Do?
Reduce your greenhouse gas emissions by choosing a car with better gas mileage.
Pollution control devices cannot reduce your car’s CO2 emissions. You can only reduce them by
- Choosing a car with better gas mileage
- Getting the best fuel economy out of your car
- Using a low-carbon fuel, such as ethanol or CNG
- Walking, biking, or taking public transit more often
- Combining trips when possible (also saves time and money)
We Can Help
Fueleconomy.gov’s Find-a-Car feature provides greenhouse gas emissions estimates for each vehicle. Two types of emissions estimates are provided:
- Tailpipe CO2: the amount of CO2 emitted directly from the vehicle and a scale that shows emissions relative to other vehicles
- Tailpipe & upstream GHG:greenhouse gas emissions (CO2, methane, and nitrous oxide) from the vehicle’s tailpipe, as well as “upstream” GHG emissions related to the production and distribution of the fuel used to power the vehicle