Reduce Climate Change

Highway vehicles release about 1.7 billion 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 GHG. That's roughly 6 to 9 tons of GHG each year for a typical vehicle. Learn more about how a gallon of gasoline can create 20 pounds of carbond dioxide.…

How can a gallon of gasoline create 20 pounds of carbon dioxide?

It seems impossible that a 6.3-pound gallon of gasoline could produce 20 pounds of carbon dioxide (CO₂) when burned. However, most of the weight of the CO₂ comes from the oxygen in the air rather than the gasoline.

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).

CO2 molecule with one carbon atom (atomic weight 12) and two oxygen atoms (atomic weight of 16 each)

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 approximately 20 pounds of CO₂!

Data Sources

Physical and chemical properties of gasoline: Department of Energy (DOE), Alternative Fuels Data Center (AFDC), Properties of Fuels.

Vehicles are responsible for over half (51%) of the carbon dioxide emissions for a typical household.

What Can I Do?

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
Purchasing green power for your electric vehicle or plug-in hybrid
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

Greenhouse Gas Emissions score example: tailpipe-only emissions

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

Greenhouse Gas Emissions score example: tailpipe and upstream emissions

More Information on Climate Change

EPA's Transportation and Climate Site

EPA's Climate Change Site

What You Can Do

Intergovernmental Panel on Climate Change (IPCC)

Global Warming: Frequently Asked Questions (National Oceanic and Atmospheric Administration [NOAA])

View Data Sources…

Highway vehicle GHG emissions based on EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 – 2011, Table 2-15. April 2013. Note: Units converted from metric to short tons.

Average annual vehicle GHG emissions based on Transportation Energy Data Book, Edition 33. Table 11.10. July 31, 2014.

Annual tons of GHG by fuel economy (MPG) are estimated using GREET Model 1.8 (U.S. Department of Energy, Argonne National Laboratory) and include primary GHGs caused by motor vehicles: carbon dioxide (CO₂), nitrous oxide (NO_x), and methane (CH₄). Assumes vehicles travel 15,000 miles per year.