Abstract: A method of recovering substantially pure CO.sub.2 from a fermentation gas polluted with organic compounds and with sulphur compounds comprising the steps of:(a) washing the gas with water or an aqueous solution in a scrubber with a packed bed until the washed gas contains no more than 2.5 ppm organic impurities;(b) oxidizing the oxidizable impurities so as to provide a gas having a level of purity such that when said gas is bubbled through mineral water there are no noticeable smell or taste deviations;(c) removing the major part of the water; and(d) drying the CO.sub.2 to the desired water content.