Abstract: A method for converting a feedstock comprising solid hydrocarbons to a sweet synthesis gas, involving the steps a. gasifying said feedstock in the presence of steam, an oxygen rich gas and an amount of sour process gas to form a raw synthesis gas optionally comprising tar, b. optionally conditioning said raw synthesis gas to a sour shift feed gas, c. contacting said sour shift feed gas with a sulfided material catalytically active in the water gas shift process for providing a sour hydrogen enriched synthesis gas, d. separating H2S and CO2 from said sour hydrogen enriched synthesis gas, for providing said sour recycle gas and a sweet hydrogen enriched synthesis gas.