A Natural gas vehicle or NGV is a alternative fuel vehicle that uses compressed natural gas (CNG) or, less commonly, liquefied natural gas (LNG) as a clean alternative to other automobile fuels. Worldwide, there are roughly 5 million NGVs as of 2006, with the largest number of NGVs in Argentina, Brazil, Iran, Pakistan and Thailand. In Europe they are popular in Germany and Italy.
NGV's can be refueled anywhere from existing natural gas lines. This makes home refuelling stations that tap into such lines possible. A company called FuelMaker has pioneered such a system known as "Phill", which they have developed in partnership with Honda. 
Existing gasoline-powered vehicles may be converted to CNG. An increasing number of vehicles worldwide are being manufactured to run on CNG (Honda Civic, Samand). GM do Brasil introduced the MultiPower engine in August 2004 which was capable of using CNG, alcohol and petrol as fuel. The GM engine has electronic fuel injection that automatically adjusts to any acceptable fuel configuration. This motor was used in the Chevrolet Astra and was aimed at the taxi market.Although a localized problem, NGV refill stations can be scarce in some places, with taxi drivers waiting in long queues to refill. This has led to suggestions that taxis should have their own options for fueling at taxi ranks - a model being tested in Casablanca, Morocco. Here, taxi drivers 'belong' to a base station where they operate from and have priority fuel rights including an account card.
The primary component of natural gas is methane (CH4), the shortest and lightest hydrocarbon molecule. It may also contain heavier gaseous hydrocarbons such as ethane (C2H6), propane (C3H8) and butane (C4H10), as well as other gases, in varying amounts. Hydrogen sulfide (H2S) is a common contaminant, which must be removed prior to most uses.