CNG – COMPRESSED NATURAL GAS
Compressed natural gas (CNG) is a fossil fuel substitute for gasoline (petrol), Diesel fuel, and propane/LPG. Although CNG’s combustion does produce greenhouse gases, it is widely considered a more environmentally “clean” alternative to conventional fuels; plus, it is much safer than other fuels in the event of a spill (as natural gas is lighter than air, and disperses quickly when released). CNG may also be mixed with biogas (produced from landfills orwastewater).
CNG is made by compressing natural gas (which is mainly composed of methane, CH4), to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of 200–248 bar (2,900–3,600 psi), usually incylindrical or spherical shapes.
CNG is used in traditional gasoline/internal combustion engine automobiles that have been converted into bi-fuel vehicles (gasoline/CNG). Natural gas vehicles are increasingly used in Iran, the Asia-Pacific region, especially in Indian capital of Delhi, and other large cities like Ahmedabad, Mumbai, Kolkata, Chennai and some other cities such as Lucknow, Kanpur etc,. Latin America, Europe, and North America due to rising gasoline prices. In response to high fuel prices and environmental concerns, CNG is starting to be used also in tuk-tuks and pickup trucks, transit and school buses, and trains.
The cost of conversion is a 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% per year).
CNG’s volumetric energy density is estimated to be 42% that of liquefied natural gas(because it is not liquefied), and 25% that of Diesel fuel.