Compressed Natural Gas Vehicles

Natural Gas as Auto Fuel

Compared to gasoline, compressed natural gas (CNG) is cleaner, less expensive, and generally comes from domestic reserves. However, CNG vehicles also require some compromises, including the use of a special refueling infrastructure that is not widely developed in the United States.

CNG vehicles store natural gas in pressurized tanks and burn the gas in slightly modified internal combustion engines. Natural gas, which is 90 percent methane, has a much higher octane rating than gasoline, allowing for higher compression ratios and therefore greater efficiency in the engines that use it. Natural gas burns so cleanly that CNG vehicles rival hybrids in producing extremely low levels of smog-forming pollutants. In 2001, the EPA declared the engine in the Honda Civic GX "the cleanest internal combustion engine on Earth." However, CNG vehicles tend to have higher greenhouse gas emissions than hybrids. The CNG version of the Civic, for example, emits nearly 30 percent more greenhouse gases than the Civic Hybrid during a typical year of driving.

Only One Choice, For Now

Natural gas is normally used in the U.S. to generate electricity, heat houses and businesses, and as a component in a variety of industrial processes. In the United States, a very small amount of natural gas (just one-tenth of 1% of all gas consumed) is also used as a fuel for vehicles. Traditionally, CNG vehicles have been used in private and government fleets, but some of these vehicles also are owned by private citizens. According to the Natural Gas Vehicle Coalition, there are 130,000 CNG vehicles in use in the United States, although this modest total includes heavy-duty vehicles (such as trucks and buses) as well as automobiles. Other countries, including Argentina and Brazil, boast more than 1 million CNG vehicles apiece.

If you’re thinking of joining the league of CNG drivers in the U.S., your choice of new vehicles is limited this year to one: The Honda Civic GX, a natural gas-powered version of the Civic. Compared with a Civic Hybrid, you’ll pay $2,290 more for the Civic GX, although you’ll be eligible for a $4,000 tax incentive, while incentives for buying a Civic Hybrid are no longer available. In addition, CNG vehicles such as the Civic GX are eligible for most of the same parking and carpool lane privileges as hybrids; in many states, CNG vehicles were using HOV lanes long before hybrids.

Another advantage of CNG vehicles is that, at least currently, the natural gas used to power them is primarily from domestic sources. According to the U.S. Department of Energy, just 20 percent of the natural gas consumed in the United States last year was imported, and most of those imports came from Canada—a country considered a supporter of terrorism far less often than several oil-producing nations that shall remain nameless. Unfortunately, natural gas imports have been rising gradually since the mid-1980s, and as demand for natural gas in the U.S. grows, the amount imported from overseas may have to grow also.