A method of producing one or more products including alcohols and/or acids by microbial fermentation, the method comprising: i. receiving gas stream(s) comprising CO from an industrial process; ii. passing the gas stream(s) to a bioreactor containing a culture of one or more carboxydotrophic bacteria in a liquid nutrient medium; and iii. fermenting the culture in the bioreactor to produce one or more products including alcohols and/or acids, wherein the gas stream(s) comprising CO is sourced from the gasification of methane or natural gas, or is derived from the steam reforming of hydrocarbons, and wherein the method further comprises capturing at least a portion of a CO 2 content, using a CO 2 remover, from one or both of: (a) a stream prior to the stream entering the bioreactor; and (b) a stream after the stream has exited the bioreactor; provided that the method is other than a method where a feed of methane (100 kmoles per hour) is passed to a steam methane reformer with steam (285 kmoles per hour) and a recycle stream of hydrogen (92 kmoles per hour), carbon monoxide (19 kmoles per hour), carbon dioxide (181 kmoles per hour) and methane (2 kmoles per hour), the steam:CO2 ratio in the reforming being 1.56:1, the reforming producing a product stream consisting of hydrogen (318 kmoles per hour), carbon monoxide (193 kmoles per hour), carbon dioxide (107 kmoles per hour), methane (2 kmoles per hour) and water (259 kmoles per hour) in the vapour phase, the product stream being cooled and the majority of the water (256 kmoles per hour) being separated from a first product stream comprising the remaining components, both the separated water and the first product stream then being passed to the fermentation step (total feed same as product stream from reforming), wherein fermentation occurs to produce 2 product streams: - a gas stream consisting of hydrogen (231 kmoles per hour), carbon monoxide (19 kmoles per hour), carbon dioxide (194 kmoles per hour), methane (2 kmoles per hour), - a liquid stream consisting of water (216 kmoles per hour) and ethanol (44 kmoles per hour), the system resulting in excess hydrogen, and thus hydrogen (139 kmoles per hour) being separated via membrane separation, the membrane separation being imperfect and removing gases in the following order of preference H2 » CO2 » CO so a minor amount of carbon dioxide (12 kmole per hour) is necessarily also removed with the hydrogen, and the remaining components (hydrogen (92 kmoles per hour), carbon monoxide (19 kmoles per hour), carbon dioxide (181 kmoles per hour) and methane (2 kmoles per hour)) being recycled to the reforming step; and provided that the method is other than a method where a feed of methane (100 kmoles per hour) is passed to a steam methane reformer with steam (70 kmoles per hour) and a recycle stream of hydrogen (82 kmoles per hour), carbon monoxide (20 kmoles per hour), carbon dioxide (109 kmoles per hour) and methane (20 kmoles per hour), the steam:CO2 ratio in the reforming being 0.65:1, the reforming producing a product stream consisting of hydrogen (298 kmoles per hour), carbon monoxide (205 kmoles per hour), carbon dioxide (25 kmoles per hour), methane (20 kmoles per hour) and water (54 kmoles per hour) in the vapour phase, the product stream being cooled and the majority of the water (51 kmoles per hour) being separated from a first product stream comprising the remaining components, both the separated water and the first product stream then being passed to the fermentation step (total feed same as product stream from reforming), wherein fermentation occurs to produce 2 product streams: - a gas product stream consisting of hydrogen (206 kmoles per hour), carbon monoxide (20 kmoles per hour), carbon dioxide (117 kmoles per hour), methane (20 kmoles per hour) and small quantities of water and ethanol, - a liquid stream consisting of 46 kmoles of ethanol and 8 kmoles of water, hydrogen (124 kmoles per hour) being separated via membrane separation from the gas stream, a minor amount of carbon dioxide (7 kmole per hour) also being removed with the hydrogen, and the remaining components (hydrogen (82 kmoles per hour), carbon monoxide (20 kmoles per hour), carbon dioxide (109 kmoles per hour) and methane (20 kmoles per hour) being recycled to the reforming step. i. receiving gas stream(s) comprising CO from an industrial process; ii. passing the gas stream(s) to a bioreactor containing a culture of one or more carboxydotrophic bacteria in a liquid nutrient medium; and iii. fermenting the culture in the bioreactor to produce one or more products including alcohols and/or acids, (a) a stream prior to the stream entering the bioreactor; and (b) a stream after the stream has exited the bioreactor; - a gas stream consisting of hydrogen (231 kmoles per hour), carbon monoxide (19 kmoles per hour), carbon dioxide (194 kmoles per hour), methane (2 kmoles per hour), - a liquid stream consisting of water (216 kmoles per hour) and ethanol (44 kmoles per hour), - a gas product stream consisting of hydrogen (206 kmoles per hour), carbon monoxide (20 kmoles per hour), carbon dioxide (117 kmoles per hour), methane (20 kmoles per hour) and small quantities of water and ethanol, - a liquid stream consisting of 46 kmoles of ethanol and 8 kmoles of water, hydrogen (124 kmoles per hour) being separated via membrane separation from the gas stream, a minor amount of carbon dioxide (7 kmole per hour) also being removed with the hydrogen, and the remaining components (hydrogen (82 kmoles per hour), carbon monoxide (20 kmoles per hour), carbon dioxide (109 kmoles per hour) and methane (20 kmoles per hour) being recycled to the reforming step.