For example, transporting petroleum and the manufacture and use of gasoline contribute heavily to air and water pollution. To solve these problems, gasoline manufacturers are developing gasolines that pollute the environment less. How gasoline is produced Most gasoline is made by separating and chemically changing the different compounds in petroleum. This process is called refining. For information on petroleum refining, see Petroleum .
Some gasoline comes from the natural gas found with petroleum.
Gasoline manufacturers remove this natural or casinghead gasoline from the natural gas. The refiners then blend the natural gasoline with other gasoline. About 5 percent of the gasoline used in the United States comes from natural gas. Gasoline can be produced by many processes and made from anything containing the elements carbon and hydrogen. One of the most promising sources of gasoline for the future involves processing the oil contained in shale rock.