Heavy residual oils are burned in large ship boilers and in electric power plants. Fuel oils are easy to transport and store, and they have twice the heating value of coal for the same weight. Today the most important gaseous fuels are natural gases from wells. They have almost entirely replaced manufactured coal and water gas. Natural gas contains light hydrocarbon compounds, mostly methane and ethane, and is used for heating and cooking in the home and for industrial heating.
Gaseous fuels are convenient because they can be readily turned on and off.
They produce no smoke and leave no ash behind. But they generally are not as easily moved about as are other fuels and, accordingly, are not useful for transportation vehicles. It is transported under pressure in refrigerated ships. When it reaches its destination, the LNG is stored in refrigerated containers at these low temperatures until it is needed. It is then allowed to evaporate back into its gaseous form for pumping into pipelines.