The Fischer-Tropsch (FT) process makes liquid fuels from gases.  The resulting fuels can be used in conventional engines with no modifications.  The gas feed can be natural gas or produced by gasification of either biomass or coal.  The two applications that have been commercialized are converting natural gas to FT diesel because diesel can be transported at much lower cost than LNG and converting coal to oil in locations where there are no local sources of oil.  The process is becoming increasingly important as petroleum resources are becoming depleted.