For both gasification and liquefaction of raw fuels into end end fuels, the chemical structure of various stages conversion is of great importance. Variations in the process design as well as the variables of a given process can be correlated with the structural parameters of fuels. Even within a given type of raw fuel, large differences occur. Optimization of the conversion process to the best end fuel should be considered (intrafuel optimization). Furthermore, it is advantageous to refine a combination of two types of raw fuels (interfuel combinations). Economics should always be relayed directly to the chemical structures of the raw fuels, whether to separation and extraction or to the environment. New in situ and biochemical recoveries should be sought. Further extension to the existing resources based on chemical knowledge could be explored.