A method of operating a fermentation process with a bioreactor containing a bacterial culture in a liquid nutrient medium, the method comprising: a. passing a C1 feedstock comprising one or both of CO and CO 2 from an industrial process to the bioreactor, wherein the C1 feedstock has a cost per unit; b. passing a gaseous CO 2 -containing substrate to an electrolyzer process to produce an electrolyzer feedstock comprising CO, and/or passing a water stream to an electrolyzer process to produce an electrolyzer feedstock comprising H 2; c. determining if the cost per unit of the electrolyzer feedstock is less than or greater than the cost per unit of the C1 feedstock, wherein the electrolyzer feedstock has a cost per unit with respect to H 2 given by the equation $ z MWh × 1 MWh 3.6 GJ electricity × x GJ electricity GJ H 2 × y GJ H 2 GJ ethanol where z represents the cost of power, x represents the electrolysis efficiency, and y represents the yield of ethanol, and the electrolyzer feedstock has a cost per unit with respect to CO given by the equation $ z MWh × 1 MWh 3.6 GJ electricity × x GJ electricity GJ CO × y GJ CO GJ ethanol where z represents the cost of power, x represents the electrolysis efficiency, and y represents the yield of ethanol; d. if the cost per unit of electrolyzer feedstock is less than the cost per unit of C1 feedstock, passing at least a portion of the electrolyzer feedstock from the electrolyzer process to the bioreactor to displace at least a portion of the C1 feedstock; and e. fermenting the culture to produce at least one fermentation product comprising ethanol, wherein the ethanol has a value per unit. a. passing a C1 feedstock comprising one or both of CO and CO 2 from an industrial process to the bioreactor, wherein the C1 feedstock has a cost per unit; b. passing a gaseous CO 2 -containing substrate to an electrolyzer process to produce an electrolyzer feedstock comprising CO, and/or passing a water stream to an electrolyzer process to produce an electrolyzer feedstock comprising H 2; c. determining if the cost per unit of the electrolyzer feedstock is less than or greater than the cost per unit of the C1 feedstock, wherein the electrolyzer feedstock has a cost per unit with respect to H 2 given by the equation $ z MWh × 1 MWh 3.6 GJ electricity × x GJ electricity GJ H 2 × y GJ H 2 GJ ethanol where z represents the cost of power, x represents the electrolysis efficiency, and y represents the yield of ethanol, and the electrolyzer feedstock has a cost per unit with respect to CO given by the equation $ z MWh × 1 MWh 3.6 GJ electricity × x GJ electricity GJ CO × y GJ CO GJ ethanol where z represents the cost of power, x represents the electrolysis efficiency, and y represents the yield of ethanol; where z represents the cost of power, x represents the electrolysis efficiency, and y represents the yield of ethanol, and the electrolyzer feedstock has a cost per unit with respect to CO given by the equation $ z MWh × 1 MWh 3.6 GJ electricity × x GJ electricity GJ CO × y GJ CO GJ ethanol where z represents the cost of power, x represents the electrolysis efficiency, and y represents the yield of ethanol; d. if the cost per unit of electrolyzer feedstock is less than the cost per unit of C1 feedstock, passing at least a portion of the electrolyzer feedstock from the electrolyzer process to the bioreactor to displace at least a portion of the C1 feedstock; and e. fermenting the culture to produce at least one fermentation product comprising ethanol, wherein the ethanol has a value per unit.