NOVELTY - Synthesis gas (7) is produced from biomass (2) by feeding a stream of pressurized biomass (5) into a gasifier (6) by a pressurizing gas in a biomass supply system for at least partial combustion of the biomass, and feeding the stream of raw product gas through gas processing devices (10, 12, 13, 14) for converting the product gas to a stream of synthesis gas. One of the processing steps comprises separating carbon dioxide (9) from the product gas in a gas processing device comprising a gas purificator (10).    USE - Method for producing a synthesis gas (claimed) for the production of liquid hydrocarbon products in a Fischer-Tropsch process.    ADVANTAGE - The carbon dioxide can be produced from the raw product gas, recycled, and recovered again before the synthesis gas is led forward. It is possible to use all of the carbon dioxide in the cycle. The pressure of the recovered carbon dioxide is in a suitable level for recycling.    DETAILED DESCRIPTION - Production of synthesis gas (7) from biomass (2) involves preparing raw product gas by feeding a stream of pressurized biomass (5) into the gasifier (6) for at least partial combustion of the biomass to obtain a stream of raw product gas (3). The biomass is fed to the gasifier by pressurizing gas in a biomass supply system (4). The stream of raw product gas is fed through gas processing devices (10, 12, 13, 14) for converting the product gas to a stream of synthesis gas. One of the processing steps comprises separating carbon dioxide (9) from the product gas in a gas processing device comprising a gas purificator (10). A stream of the carbon dioxide is fed to at least one part of the apparatus from biomass supply system, gasifier, and at least one of the gas processing devices. An INDEPENDENT CLAIM is included for an apparatus for producing synthesis gas.    DESCRIPTION OF DRAWING(S) - The drawing is a sectional view of an apparatus for producing a synthesis gas.    Biomass (2)    Raw product gas (3)    Biomass supply system (4)    Pressurized biomass (5)    Gasifier (6)    Synthesis gas (7)    Carbon dioxide (9)    Gas purificator (10)    Gas processing devices (10, 12, 13, 14)