Gaseous fuel in the context of "Liquefaction of gases"

A motor fuel is a fuel that is used to provide power to the engine (motor) of vehicles — typically a heat engine that produces thermal energy via oxidative combustion of liquid or gaseous fuel and then converts the heat into mechanical energy through reciprocating pistons or gas turbines.

Currently, the majority of motor vehicles, powerboats and light aircraft worldwide are propelled by internal combustion engines powered by petroleum-based hydrocarbon fossil fuels such as gasoline, diesel or autogas, while larger ships and aircraft use marine diesel oil and kerosene to power gas/steam turbine, turboprop and jet engines. Other fuel types include ethanol, biodiesel, biogasoline, propane, compressed natural gas (CNG) and hydrogen (either using fuel cells or hydrogen combustion). There are also cars that use a hybrid drivetrain of different power sources. The use of synthetic alternative fuels (especially renewable biofuels) is increasing, especially in Europe, as well as increasing mass adoption of battery electric vehicles (which are powered by battery-stored electricity instead of fuels).

Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid.Most liquid fuels in widespread use are derived from fossil fuels; however, there are several types, such as hydrogen fuel (for automotive uses), ethanol, and biodiesel, which are also categorized as a liquid fuel. Many liquid fuels play a primary role in transportation and the economy.

Liquid fuels are contrasted with solid fuels and gaseous fuels.

Solid fuel refers to various forms of solid material that can be burnt to release energy, providing heat and light through the process of combustion. Solid fuels can be contrasted with liquid fuels and gaseous fuels. Common examples of solid fuels include wood, charcoal, peat, coal, hexamine fuel tablets, dry dung, wood pellets, corn, wheat, rice, rye, and other grains. Solid fuels are extensively used in rocketry as solid propellants. Solid fuels have been used throughout human history to create fire and solid fuel is still in widespread use throughout the world in the present day.

Solid fuel from biomass is regarded as a renewable energy source which can contribute to climate change mitigation efforts. Solid fuel from fossil fuels (i.e. coal) is not a renewable energy.