Process for the production of liquid hydrocarbons from a feedstock that comprises at least one elementary feedstock from the group of biomass, coal, lignite, petroleum residues, methane, and natural gas, comprising: at least one stage a) for gasification of the feedstock by partial oxidation and/or steam reforming to produce a synthesis gas SG; a stage b) for separating CO2 from SG and a portion of the effluent of the subsequent stage c); the mixing of a portion of the CO2 that is separated with a gas of an H2/CO ratio of more than 3; a stage c) for partial conversion with hydrogen, thermal or thermocatalytic, of the CO2 that is present in said first mixture according to the reaction: CO2+H2→CO+H2O in a specific reaction zone that is separated from said gasification zone or zones; a stage d) for Fisher-Tropsch synthesis on a synthesis gas that comprises at least a portion of SG and at least a portion of the CO that is produced by the conversion of CO2 into hydrogen.