CNG

Compressed natural gas (CNG) is natural gas, predominantly methane, that has been compressed to high pressures for storage and use as a fuel. In vehicle applications, CNG is stored in lightweight cylinders at pressures around 20 to 25 MPa (200–250 bar). For stationary use, lower pressures may be employed. Natural gas is odorized with odorants to aid leak detection.

CNG is produced by processing natural gas to remove impurities and water, then compressed at fueling stations or refilling depots before distribution to fueling sites. Refueling involves fast or incremental compression, with safety features to monitor pressure, temperature, and leaks. Standards from organizations such as ISO and SAE govern CNG storage, fueling interfaces, and cylinder construction.

As a motor fuel, CNG is used in light- and heavy-duty vehicles, including passenger cars, taxis, buses, and trucks, as well as in some fleets for power generation or on-site cogeneration. Advantages include lower fuel cost per energy unit in many markets, cleaner combustion with reductions in particulate matter and some pollutants compared with gasoline or diesel, and compatibility with existing natural gas supply. Disadvantages include lower energy density by volume, requiring larger or multiple high-pressure tanks, limited fueling infrastructure, and methane's potency as a greenhouse gas in the event of leaks.

Global adoption varies by region; CNG networks are well established in parts of Asia, Europe, and the Americas, with ongoing expansion in urban areas and transport fleets. The technology is supported by policy incentives, supplier networks, and ongoing improvements in cylinder materials and compressing equipment.