A method for manufacturing biomass based fuel, the method comprising - providing solid biomass into a reactor, - providing steam into the reactor, - maintaining said biomass and said steam simultaneously in the reactor, in a pressure of at least 10 bar(a) and at a temperature from 180 °C to 250 °C for at least 2 minutes; - decreasing the pressure in the reactor and/or conveying biomass out of the reactor such that the pressure of the environment of the biomass decreases below 5 bar(a), to produce steam-exploded biomass, - adding a combustion additive to the biomass and/or the steam-exploded biomass such that the amount of the combustion additive is at least 0.1 w-% and at most 16 w-% of the amount of the biomass based fuel, wherein - the combustion additive is selected from a group consisting of aluminium silicates of any type such as andalusite, kyanite, sillimanite, kaolinite, metakaolinite, and mullite; chalk such as limestone (CaCO 3); clay such as kaolin, rolovite, or bentonite; dolomite (CaMg(CO 3) 2), magnesium carbonate (MgCO 3), coal fly ash, aluminium sulphate, mono calcium phosphate, dicalcium phosphate, calcite, bauxite, bentonite, bauxite, emalthite, gibbsite, hectorite, halloysite, and sulphur, or the combustion additive comprises at least one of calcium (Ca), magnesium (Mg), potassium and phosphorus, optionally bound to other elements; and - at least some of the combustion additive is added to steam-exploded biomass after the reactor and - the combustion additive is added to the steam-exploded biomass when the temperature of the steam-exploded biomass is at least 90 °C and/or - at least some of the combustion additive is added into the reactor. - providing solid biomass into a reactor, - providing steam into the reactor, - maintaining said biomass and said steam simultaneously in the reactor, in a pressure of at least 10 bar(a) and at a temperature from 180 °C to 250 °C for at least 2 minutes; - decreasing the pressure in the reactor and/or conveying biomass out of the reactor such that the pressure of the environment of the biomass decreases below 5 bar(a), to produce steam-exploded biomass, - adding a combustion additive to the biomass and/or the steam-exploded biomass such that the amount of the combustion additive is at least 0.1 w-% and at most 16 w-% of the amount of the biomass based fuel, wherein - the combustion additive is selected from a group consisting of aluminium silicates of any type such as andalusite, kyanite, sillimanite, kaolinite, metakaolinite, and mullite; chalk such as limestone (CaCO 3); clay such as kaolin, rolovite, or bentonite; dolomite (CaMg(CO 3) 2), magnesium carbonate (MgCO 3), coal fly ash, aluminium sulphate, mono calcium phosphate, dicalcium phosphate, calcite, bauxite, bentonite, bauxite, emalthite, gibbsite, hectorite, halloysite, and sulphur, or the combustion additive comprises at least one of calcium (Ca), magnesium (Mg), potassium and phosphorus, optionally bound to other elements; and - at least some of the combustion additive is added to steam-exploded biomass after the reactor and - the combustion additive is added to the steam-exploded biomass when the temperature of the steam-exploded biomass is at least 90 °C and/or - at least some of the combustion additive is added into the reactor.