Compressed natural gas
Compressed natural gas (CNG) (methane stored at high pressure) is a fuel which can be used in place of gasoline, diesel fuel and propane/LPG. CNG combustion produces fewer undesirable gases than the aforementioned fuels. In comparison to other fuels, natural gas poses less of a threat in the event of a spill, because it is lighter than air and disperses quickly when released. Biomethane Ц cleaned-up biogas from anaerobic digestion or landfills Ц can be used.
The cost and placement of fuel storage tanks is the major barrier to wider/quicker adoption of CNG as a fuel. It is also why municipal government, public transportation vehicles were the most visible early adopters of it, as they can more quickly amortize the money invested in the new (and usually cheaper) fuel. In spite of these circumstances, the number of vehicles in the world using CNG has grown steadily (30 percent per year). Now, as a result of the industry's steady growth, the cost of such fuel storage tanks has been brought down to a much more acceptable level. Especially for the CNG Type 1 and Type 2 tanks, many countries are able to make reliable and cost effective tanks for conversion need.
Several manufacturers (Fiat, Opel/General Motors, Peugeot, Volkswagen, Toyota, Honda and others) sell bi-fuel cars. In 2006, Fiat introduced the Siena Tetrafuel in the Brazilian market, equipped with a 1.4L FIRE engine that runs on E100, E25 (Standard Brazilian Gasoline), Ethanol and CNG.
CNG locomotives are operated by several railroads. The Napa Valley Wine Train successfully retrofit a diesel locomotive to run on compressed natural gas before 2002. This converted locomotive was upgraded to utilize a computer controlled fuel injection system in May 2008, and is now the Napa Valley Wine Train's primary locomotive. Ferrocarril Central Andino in Peru, has run a CNG locomotive on a freight line since 2005. CNG locomotives are usually diesel locomotives that have been converted to use compressed natural gas generators instead of diesel generators to generate the electricity that drives the traction motors. Some CNG locomotives are able to fire their cylinders only when there is a demand for power, which, theoretically, gives them a higher fuel efficiency than conventional diesel engines. CNG is also cheaper than petrol or diesel.
The lack of harmonized codes and standards across international jurisdictions is an additional barrier to NGV market penetration. The International Organization for Standardization has an active technical committee working on a standard for natural gas fuelling stations for vehicles.
Colombia had an NGV fleet of 300,000 vehicles, and 460 refueling stations, as of 2009. Bolivia has increased its fleet from 10,000 in 2003 to 121,908 units in 2009, with 128 refueling stations. Peru had 81,024 NGVs and 94 fueling stations as 2009, but that number is expected to skyrocket as Peru sits on South America's largest gas reserves. In Peru several factory-built NGVs have the tanks installed under the body of the vehicle, leaving the trunk free. Among the models built with this feature are the Fiat Multipla, the new Fiat Panda, the Volkswagen Touran Ecofuel, the Volkswagen Caddy Ecofuel and the Chevy Taxi. Other countries with significant NGV fleets are Venezuela (15,000) and Chile (8,064) as of 2009.
