The present invention provides a process for the manufacture of a useful product from synthesis gas having a desired hydrogen to carbon monoxide molar ratio comprising: gasifying a first carbonaceous feedstock comprising waste materials and/or biomass in a gasification zone to produce a first synthesis gas; optionally partially oxidising the first synthesis gas in a partial oxidation zone to generate oxidised synthesis gas; reforming a second carbonaceous feedstock to produce a second synthesis gas, the second synthesis gas having a different hydrogen to carbon ratio from that of the first raw synthesis gas; combining at least a portion of the first synthesis gas and at least a portion of the second synthesis gas in an amount to achieve the desired hydrogen to carbon molar ratio and to generate a combined synthesis gas and subjecting at least part of the combined synthesis gas to a conversion process effective to produce the useful product. The reforming step enables the conventional water gas shift reaction to be dispensed with.