Find the green car that is just right

Looking to reduce your carbon footprint? Your car is an obvious place to start. While standard, gas-fueled cars dominate the roads, there are a few current alternatives and some promising future technologies.

Natural gas is commonly used in the United States to heat homes and water, and fuel ovens and stoves. It can also fuel internal combustion engines, usually as compressed natural gas. Vehicles using CNG produce 15 percent to 20 percent less carbon dioxide than gasoline cars, although they release a lesser amount of methane, another greenhouse gas. Of the regulated emissions, CNG cars produce substantially less carbon monoxide and nitrogen oxide than similar gasoline cars. The California Air Resource Board classifies the Honda's Civic GX as an Advanced Technology Partial Zero Emissions Vehicle, which means it has extraordinarily low smog-causing emissions.

One reason for CNG's reduced carbon dioxide output over gasoline is that it has the highest ratio of energy over carbon content of any fossil fuel. On the downside, because it's a gas, CNG requires more space for a quantity equivalent to a gallon of gasoline, resulting in larger tanks. Natural gas is currently cheaper than gasoline, and mostly produced domestically, but finding a filling station can be difficult. Honda showed off a home filling station, which taps natural gas lines that are part of public utilities infrastructure, at recent auto shows. Other natural gas filling stations appropriate for vehicles can be found on the Department of Energy's Alternative Fuel Locator Web site.

Read about the Civic GX.

Because of the few natural gas refilling stations, most natural gas vehicles are in fleets, both private and government. Few car companies make a production model for the United States market, so most are conversions. To get a CNG-powered car, buyers can either get the Honda Civic GX or look for a used car from a fleet.

More green car resources from CNET