NOVELTY - Producing hydrocarbon composition, comprises: providing biomass raw-material; gasifying raw-material by oxygen-blown gasification to produce raw syngas containing carbon monoxide, carbon dioxide, hydrogen, hydrocarbons and gaseous and particulate impurities; removing at least an essential part of impurities to produce clean syngas; feeding clean syngas to Fischer-Tropsch (FT) reactor (3); converting, in FT reactor, at least a significant part of carbon monoxide and hydrogen in syngas into the hydrocarbon composition containing 4-90C hydrocarbons; and recovering the composition from FT reactor.    USE - The method is useful for producing a hydrocarbon composition (claimed), which is useful for producing fuel for combustion engines.    ADVANTAGE - The method: provides the hydrocarbon composition, which exhibits increased hydrogen to carbon monoxide ratio and is free from impurities; and requires less energy, when compared with conventional methods.    DETAILED DESCRIPTION - Producing a hydrocarbon composition, comprises: providing a biomass raw-material; gasifying the raw-material by oxygen-blown gasification to produce a raw syngas containing carbon monoxide, carbon dioxide, hydrogen, hydrocarbons and gaseous and particulate impurities, where the raw syngas has a hydrogen-to-carbon monoxide ratio of 0.5-1.7; removing at least an essential part of the impurities to produce a clean syngas; feeding the clean syngas to a Fischer-Tropsch (FT) reactor (3); converting, in the FT reactor, at least a significant part of the carbon monoxide and hydrogen contained in the syngas into the hydrocarbon composition containing 4-90C hydrocarbons; and recovering the hydrocarbon composition from the FT reactor, where the composition mainly contains hydrocarbons that are solid or semisolid at ambient temperature and pressure. The hydrogen-to-carbon monoxide ratio of the syngas is being raised to 2 at the latest when the syngas is fed into the FT reactor, by (a) separately recovering an off-gas from the FT reactor, where the off-gas comprises hydrocarbons that are gaseous at ambient temperature and pressure, (b) producing hydrogen from the gaseous hydrocarbons of the off-gas and/or (c) feeding at least a part of the hydrogen gas thus produced into the clean syngas in order to increase the hydrogen-to-carbon monoxide ratio of the clean syngas.    DESCRIPTION OF DRAWING(S) - The figure shows the process of producing a hydrocarbon composition.    Upstream processing steps (1)    Increasing hydrogen to carbon monoxide ratio (2)    Fischer-Tropsch reactor (3)    Reforming reaction (4)    Shift reaction (5)