A method of operating a gas turbine power plant and gas turbine power plant are disclosed wherein hydrogen for the combusting process is produced by feeding natural gas mixed with steam through a membrane/partial oxidation reactor and converting the natural gas at least to H2 and CO. Thereby oxygen is transferred from the compressed air through the membrane of the membrane/partial oxidation reactor and the oxygen is used for the partial oxidation process of the natural gas. The process is followed by converting the syngas in a CO shift reactor and a CO shift reactor to a CO2 removal equipment to mainly hydrogen.