A system and method for producing synthesis gas

Disclosed is a method for producing synthesis gas. The method comprises the steps of: - feeding biomass (3) with an ash content above 3% by mass to a pyrolyzer (2) arranged to pyrolyze biomass (3) with an ash content above 3%, wherein said ash content is determined according to ASTM E1755-01 "Standard method for 5 the determination of ash in biomass" of 2003 Annual Book of ASTM Standards, vol. 11.05, (Philadelphia, PA), - feeding pyrolysis gas from said pyrolyzer (2) arranged to pyrolyze biomass (3) with an ash content above 3% to a partial oxidation reactor (5) to produce partially oxidized pyrolysis gas,10 - feeding biomass (17) with an ash content below 2% by mass to a pyrolyzer (8) arranged to pyrolyze biomass with an ash content below 2% by mass, and wherein pyrolysis gas from said pyrolyzer (8) arranged to pyrolyze biomass with an ash content below 2% is also fed to said partial oxidation reactor (5) to produce partially oxidized pyrolysis gas, wherein the ash content is determined 15 according to ASTM E1755-01 "Standard method for the determination of ash in biomass" of 2003 Annual Book of ASTM Standards, vol. 11.05, (Philadelphia, PA), - feeding coke (9) produced from said biomass (17) with an ash content below 2% by mass from said pyrolyzer (8) arranged to pyrolyze biomass with an ash 20 content below 2% by mass to a gasifier (7) arranged to gasify coke (9) produced from biomass (17) with an ash content less than 2% by mass, - feeding said partially oxidized pyrolysis gas through said coke (9) being produced from biomass (17) with an ash content below 2% in said gasifier (7) arranged to gasify coke (9) produced from biomass with an ash content less 25 than 2% by mass such that tar is removed from said partially oxidized gas and whereby synthesis gas is produced. Furthermore, a system (1) for producing synthesis gas is disclosed.