Unlike gasification technologies, liquefaction technologies are more at the developmental stage. For both coal and biomass there are direct and indirect methods for producing liquid products. The indirect methods are based on the use of a syngas platform from which liquid fuels and methanol can be pro­duced using Fischer-Tropsch syntheses employing different types of catalyst. Both biosyngas and petroleum — (or coal-) derived syngas can be obtained from coal-biomass mixture gasification. This subject has already been discussed in detail. The gas-to-liquid conversion process via FT synthesis depends strictly on purity and syngas composition irrespective of its generation source.

In this section we address direct methods for producing liquids from bio­mass and coal. There are three basic methods for liquid production: (a) direct liquefaction, (b) low severity pyrolysis, and (c) supercritical extraction and liquefaction. Methods (a) and (c) can be carried out either by an organic sol­vent or by water. We briefly evaluate both options.