Other meanings of Compressed natural gas
ENERGY & TRANSPORT
Compressed natural gas (CNG) is natural gas compressed for use as a vehicle fuel and energy source. It consists mainly of methane and is stored in high-pressure cylinders, where its gaseous form distinguishes it from liquefied natural gas (LNG). CNG powers passenger cars, buses, refuse trucks, delivery fleets, and some stationary equipment, especially where a local refueling network is available.
Compressed natural gas is methane-rich natural gas stored at high pressure rather than chilled into a liquid. Raw natural gas is processed to remove water, particulates, and unwanted compounds before compression; pipeline-quality gas commonly contains methane with smaller amounts of ethane, propane, nitrogen, and carbon dioxide.1 CNG occupies far less volume than gas at atmospheric pressure, but it still requires substantially more storage space than liquid fuels for the same energy content. Vehicle cylinders are commonly filled to about 3,600 pounds per square inch, or 250 bar, and are built from steel, aluminum, or composite materials. An odorant is generally added to distributed natural gas so leaks can be detected by smell.
CNG vehicles use engines adapted for gaseous fuel, usually spark-ignition engines with dedicated or bi-fuel configurations. Fuel passes from high-pressure cylinders through regulators that reduce pressure before injection into the engine; electronic controls adjust the mixture and ignition timing. Refueling may be fast fill, which resembles conventional fueling, or time fill, in which vehicles are connected for several hours and filled gradually. Time fill is particularly practical for buses and fleet vehicles that return to a depot overnight.1 CNG stations may draw gas from a utility pipeline, compress it on site, and dispense it through storage banks. Fleet operators often adopt CNG because predictable routes can offset the cost of cylinders, compressors, and dedicated maintenance equipment.
CNG combustion generally produces fewer tailpipe emissions of particulate matter and certain smog-forming pollutants than gasoline or diesel, although the outcome depends on the engine, controls, vehicle age, and comparison fuel.2 Its climate advantage is not automatic: methane is a potent greenhouse gas, and leakage during production, processing, transmission, compression, or fueling can reduce or erase the benefit of burning it instead of petroleum fuels.3 Because methane is lighter than air, an outdoor leak tends to disperse upward, while an enclosed accumulation can create a fire or explosion hazard. Cylinders require inspection and replacement on specified schedules, and damaged tanks must be handled by trained personnel. Limited station coverage, reduced cargo space, and the weight and cost of pressure vessels remain practical constraints.
CNG is also used beyond private cars, with municipal buses, refuse vehicles, taxis, airport shuttles, and short-haul trucks representing important niche applications. Renewable natural gas (RNG), produced from landfills, wastewater treatment, or agricultural waste, can be cleaned to pipeline quality and compressed for the same equipment; the vehicle fuel is still chemically methane, but its production pathway differs from fossil natural gas.4 CNG can support energy resilience when a facility has access to a gas pipeline and backup compression, although a power outage may disable compressors unless emergency systems are available. Unlike LNG, CNG does not require cryogenic storage, making it simpler for many local fleets, but its lower volumetric energy density makes long-distance vehicle storage more demanding. Standards address cylinder design, fueling connectors, inspection, and station safety.
CNG performance and environmental impacts vary with fuel composition, vehicle technology, infrastructure, and methane leakage across the supply chain.
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