Compressed natural gas
Traditional gasoline is derived from petroleum, which the United States imports heavily. In 2012, according to the Department of Energy, the U.S. imported approximately 40 percent of its petroleum. Further, more than 70 percent of the nation's total petroleum supply (imports and exports) was used for transportation purposes. Natural gas, on the other hand, is widely available in the U.S., with between 80 and 90 percent of the nation's supply produced domestically. Transitioning from traditional gasoline to compressed natural gas could reduce the nation's dependence on foreign oil.
Compressed natural gas has been shown to produce fewer harmful emissions than traditional gasoline. According to the California Energy Commission's Consumer Energy Center, compressed natural gas "[shows] an average reduction in ozone-forming emissions of 80 percent compared to gasoline vehicles." The Department of Energy and the Environmental Protection Agency report that compressed natural gas produces approximately 20 to 45 percent fewer smog pollutants and 5 to 9 percent fewer greenhouse gas emissions than traditional gasoline. In addition, compressed natural gas produces no evaporative emissions, which gasoline does.
According to CNG Now, a compressed natural gas advocacy group, the average price of compressed natural gas per gasoline gallon equivalent (GGE) was $2.11 as of September 2014, 46.5 percent less than gasoline ($3.39 per gallon) and 59.3 percent less than diesel fuel ($3.89 per gallon). Natural gas vehicles, however, typically have more limited riving ranges than their traditional gas counterparts, owing to the fact that "less overall energy content can be stored in the same size tank as the more energy-dense gasoline or diesel fuels."
The table below lists average compressed natural gas prices by state.
|Compressed natural gas prices by state, September 20141|
|State||Price per GGE2|
| 1Data not available for Hawaii, Maine, South Dakota and Vermont.|
2Gasoline gallon equivalent.
Source: CNG Now, "Average Price," accessed September 17, 2014.
According to CNG Now, in the U.S. there are roughly 250,000 natural gas vehicles currently in use. Between 2000 and 2014, the natural gas vehicle market grew by an average of 3.7 percent per year (compared to the global growth rate of 30.6 percent per year). Most natural gas vehicles are heavy-duty vehicles, such as buses and trucks. The availability of light-duty natural gas vehicles remains limited.
Traditional gasoline vehicles can be retrofitted for compressed natural gas.
Fueling stations dispensing compressed natural gas remain relatively rare, with approximately 500 operating in the U.S. as of September 2014.
- See also: Fracking
Hydraulic fracturing, or fracking, is the process of injecting fluid -- mostly water and sand (or proppant), but with additional chemicals -- into the ground at a high pressure in order to fracture shale rocks to release the hydrocarbons, including natural gas, inside. It is the use of hydraulic fracturing, in combination with horizontal drilling, that has led to a boom in natural gas production by making access to the oil and gas in shale formations commercially viable. This natural gas boom has, in turn, prompted further discussion of compressed natural gas as an alternative fuel. In some cases, a combination of water, chemicals and sand is injected into horizontally drilled wells at high speeds and pressures until gas begins to flow. Fracking can be done inside traditional vertical wells also. Fracking can also release trapped oil and water, known as produced water.
This practice is controversial as many of the chemicals used are alleged by opponents to be toxic or carcinogenic. Those activists that are against the method argue that it releases methane and harmful chemicals into nearby ground water.
- U.S. Department of Energy - Alternative Fuels Data Center, "Natural Gas," accessed September 17, 2014
- U.S. Energy Information Administration, “Glossary, C” accessed January 29, 2014
- FuelEconomy.gov, "Natural gas," accessed September 17, 2014
- U.S. Department of Energy - Alternative Fuels Data Center, "Natural Gas Fuel Basics," accessed September 17, 2014
- U.S. Department of Energy - Alternative Fuels Data Center, "Natural Gas Benefits and Considerations," accessed September 17, 2014
- California Energy Commission Consumer Energy Center, "Compressed Natural Gas (CNG) as a Transportation Fuel," accessed September 17, 2014
- CNG Now, "Average Price," accessed September 17, 2014
- CNG Now, "What is CNG?" accessed September 17, 2014
- U.S. Energy Information Administration, “Energy in Brief,” accessed January 28, 2014
- Frack Wire, “What is Fracking,” accessed January 28, 2014