"NGV" redirects here. For the art gallery in Melbourne, Australia, see National Gallery of Victoria. Learn more This article has multiple issues. Please help improve it or discuss these issues on the talk page. Truck running with Guidetti CNG system Fueling (Fiat Multipla) 2009 Honda Civic GX hooked up to Phill refueling system. A natural gas vehicle (NGV) is an alternative fuel vehicle that uses compressed natural gas (CNG) or liquefied natural gas (LNG). Natural gas vehicles should not be confused with vehicles powered by LPG (mainly propane), which is a fuel with a fundamentally different composition. In a natural gas powered vehicle, energy is released by combustion of essentially methanegas (CH 4) fuel with oxygen (O 2) from the air to carbon dioxide (CO 2) and water vapor (H 2O) in an internal combustion engine. Methane is the cleanest burning hydrocarbon and many contaminants present in natural gas are removed at source. Existing gasoline-powered vehicles may be converted to run on CNG or LNG, and can be dedicated (running only on natural gas) or bi-fuel (running on either gasoline or natural gas). Diesel engines for heavy trucks and busses can also be converted and can be dedicated with the addition of new heads containing spark ignition systems, or can be run on a blend of diesel and natural gas, with the primary fuel being natural gas and a small amount of diesel fuel being used as an ignition source. It is also possible to generate energy in a small gas turbine and couple the gas engine or turbine with a small electric battery to create a hybrid electric motor driven vehicle. Convenient and cost effective gas storage and fuelling is a key challenge compared to petrol and diesel vehicles since the natural gas is pressurized and/or - in the case of LNG - the tank needs to be kept cold. The lower energy density of gases compared to liquid fuels is mitigated to a great extent by high compression or gas liquefaction, but requires a trade-off in terms of size/complexity/weight of the storage container, range of the vehicle between refueling stops, and time to refuel. Although similar storage technologies may be used for and similar compromises would apply to a hydrogen vehicleas part of a proposed new hydrogen economy, methane as a gaseous fuel is safer than hydrogen due to its lower flammability, low corrosivity and better leak tightness due to larger molecular weight/ size, resulting in lower price hardware solutions based on proven technology and conversions. Many other factors hold back NGV popularization for individual mobility applications, i.e. private vehicles, including the cost of new vehicles, additional weight, unfamiliarity with the technology, lack of refueling and storage infrastructure, and lack of supply due to relatively small demand compared with other petroleum-based fuels such as gasoline and diesel. Worldwide, there were 24.452 million NGVs by 2016, led by China (5.0 million),  Iran (4.00 million),  India (3.045 million),  Pakistan (3.0 million),  Argentina (2.295 million),  Brazil (1.781 million), and Italy (1.001 million).[1]