TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: Producing the hydrocarbon composition comprises producing hydrogen gas from the gaseous hydrocarbons of the off-gas by subjecting them to at least one reforming reaction and to at least one shift reaction outside the main syngas stream; and producing hydrogen gas from the gaseous hydrocarbons of the off-gas by subjecting the hydrocarbons to at least one reforming reaction and to at least one shift reaction, the reactions being carried out in a cascade in the indicated order. The hydrogen gas produced from the hydrocarbons is introduced into the syngas before a gas treatment step in which carbon dioxide is removed from the syngas. The carbon dioxide is separated from the syngas by membrane filtration, by pressure swing absorption or by washing with a liquid, such as methanol, capable of absorbing carbon dioxide. Significantly all of the carbon dioxide contained in the gas is removed before it is fed into the Fischer-Tropsch reactor. The pressure of the syngas is increased to the pressure of the Fischer-Tropsch reaction immediately before, during or after the gas treatment step. The hydrocarbons of the off-gas of the Fischer-Tropsch reactor comprise saturated or unsaturated, linear or branched 1-4C hydrocarbons, in particular saturated 1-4C hydrocarbons, such as methane. Moreover, at least a part, preferably a majority, based on the volume, of the recovered gaseous hydrocarbons is recycled from the Fischer-Tropsch reactor to the syngas via at least one step in which light hydrocarbons, primarily methane, are converted to hydrogen. External light hydrocarbons, in particular 1-4C hydrocarbons, such as methane, are fed into the recovered gaseous hydrocarbons which are being recycled to the syngas before the hydrocarbons are subjected to a step for converting light hydrocarbons into hydrogen. The ratio of external methane to the methane present in the recycled gas is, based on volume, 1:100 to 100:1, in particular 1:50 to 50:1, for example 1:20 to 20:1. The method comprises: gasifying the raw-material in the presence of oxygen to produce a gas containing carbon monoxide, carbon dioxide, hydrogen and hydrocarbons possibly together with inert components; feeding the gas obtained by gasification of the raw-material into a reformer; reforming the gas in the presence of oxygen at a temperature in excess of 850 degrees C in order to increase the ratio of hydrogen to carbon monoxide in a gaseous effluent of the reformer to a value in the range of 0.5 to 1.7; withdrawing the gaseous effluent from an outlet of the reformer; cooling the gaseous effluent to a temperature below 500 degrees C; washing the gaseous effluent in a water scrubber at a pressure of 80-4000 kPa using water of a temperature in the range of 30-80 degrees C, in particular 40-60 degrees C to remove ammonia (NH3), hydrochloride (HCl) and particles; further remove hydrogen sulfide (H2S) and carbon dioxide (CO2) in a one step or two step process; and further increasing the hydrogen-to-carbon monoxide ratio of the gaseous effluent to a value of about 2 by introducing hydrogen in it. EXAMPLE - No example given.