Leg press, deadlifts, RDLs, lunges, leg extensions, leg curls, hack squats, split squats. All those will hit your legs, plus there variations. Do some sprints, run hills, stairs, those will hit your legs. Im sure there are more lifts I can't think of this second as well.
While natural gas occurs in nature as a mixture of methane and other gases, propane is actually a byproduct of both petroleum refining and natural gas processing.
Propane is not to be confused with Natural Gas, which is primarily Methane. When Natural Gas is extracted from the ground it may also contain Ethane, Propane, Butane, and Pentane, although most of these are usually stripped out for other specific applications before it is passed along through the pipelines. Impurities are also removed, including water and sulphur.