Topic summary
Compressed natural gas
Compressed natural gas (CNG) is fuel gas composed primarily of methane (CH4), compressed to less than 1% of its volume at standard atmospheric pressure. It is stored in high-pressure containers at approximately 20–25 megapascals (2,900–3,600 psi; 200–250 bar), typically in cylindrical or spherical shapes.
CNG is used in modified petrol and internal combustion engine vehicles as well as purpose-built CNG vehicles. These include dedicated CNG systems, dual-fuel vehicles that combine CNG with liquid fuel, and bi-fuel vehicles. It can serve as an alternative to petrol, diesel fuel, and liquefied petroleum gas (LPG). Compared with these fuels, CNG combustion produces lower emissions of several pollutants. Because natural gas is lighter than air, it disperses more readily when released. Biomethane derived from anaerobic digestion or landfill sources can also be used.
CNG has been used in applications including auto rickshaws, pickup trucks, transit and school buses, and trains. Municipal fleets and public transport operators have often adopted the fuel for cost and infrastructure reasons. However, fuel storage and cylinder cost remain significant factors affecting wider adoption.