This paper examines how carbon-rich gases from steelmaking can be turned into useful chemicals rather than released into the atmosphere. This study focuses on using microbes to ferment carbon monoxide from blast furnace gas and produce volatile fatty acids, which are widely used in fuels, plastics and chemicals. The paper shows that continuously removing these acids during fermentation, using a combination of membrane-based separation techniques, greatly increases how much can be produced and reduces unwanted by-products. Tested at pilot scale inside a working steel plant, this approach achieved much higher yields and enabled real-time monitoring of performance. This paper demonstrates a practical new route for reusing steelmaking emissions.