CNG stands for compressed natural gas (i.e., methane). Worldwide, there are
about 23 million vehicles that use compressed natural gas as their fuel, led by
China with 5 million such vehicles. In the Latin American region, almost 90% of
natural gas vehicles (NGVs) have bi-fuel engines, allowing these vehicles to run
on either gasoline or CNG.
Pros
■ Lighter-than-air, natural gas dissipates in an accident, making it safer than
flammable liquid fuel.
■ Natural gas is about half the price of gasoline. A gasoline-powered car
averages 32 miles per gallon while a CNG-powered car averages 43 miles
per gallon.
■ Over 90% of the natural gas that Americans use comes from domestic
sources.
■ In some states, NGVs can use a High Occupancy Vehicle (HOV) lane
anytime.Cons
■ Very few CNG-powered vehicles are available in the U.S.
■ CNG-powered vehicles cost about $5,000 more than a gasoline-powered
counterpart.
■ CNG-powered vehicles have less driving range than gasoline-powered
vehicles.
■ There are about 1,000 CNG fueling stations across the U.S., but only 536
are available for public use, and the majority are clustered around major
metropolitan hubs.
■ Home refueling devices are expensive.
■ Natural gas is a nonrenewable fossil fuel with supplies expected to last
about 90 years, although biogas is a renewable option.ELECTRIC CARS (PEVS AND HEVS)
An electric car is an automobile that is propelled by only an electric motor and
by using electrical energy stored in batteries. Electric cars were popular in the
late 19th century and early 20th century until they gave way to internal-
combustion vehicles that use gasoline. A liter of gasoline provides at least 100
times the energy of a battery taking up the same space. This extraordinary energy