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).
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!
Physical and chemical properties of gasoline: Department of Energy (DOE), Alternative Fuels Data Center (AFDC), Properties of Fuels.
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:
More Information on Climate Change
Greenhouse Gas Emissions from a Typical Passenger Vehicle (EPA Green Vehicle Guide)
Global Climate Change (NASA)
- Climate Change 2014: Synthesis Report - Summary for Policymakers
- Climate Change 2014: Mitigation of Climate Change. Chapter 8: Transport
- The Regional Impacts of Climate Change: An Assessment of Vulnerability
Highway vehicle GHG emissions based on EPA's Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 – 2018, Table 2-13. 2020. Note: Units converted from metric to short tons.
Average annual vehicle GHG emissions based on Transportation Energy Data Book, Edition 38. Table 12.11. April 2020.
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 (NOx), and methane (CH4). Assumes vehicles travel 15,000 miles per year.