Synthesis gas fermentation is a promising route for the valorization of steel mill off-gas and for replacing conventional fossil-based isopropyl alcohol (IPA) production. A recent 120 L pilot-scale study reported 85% gas conversion at 90% product selectivity and claimed a negative global warming potential (GWP) without detailed process design. The current paper reports a first-of- a- kind industrial-scale syngas fermentation process that was designed using extractive distillation with glycerol to produce 46 kton year−1 of 99.1 wt% IPA. The sustainability of an industrial-scale continuous syngas-to- IPA process has not yet been assessed. This study describes the first integrated cradle-to- gate technoeconomic analysis (TEA) and life cycle assessment (LCA), accounting for all emissions scopes, crediting prevented CO2 emissions from steel mill off gas, and including steel mill heat replacement. Parametric assessment identified higher CO volumetric mass transfer rate (VMTCO) and lower dilution rate (D) as key parameters for enhanced sustainability. For improved process design, economic and environmental tradeoffs were observed for lower glycerol bleed and higher VMTCO. At best, a −44.4% GWP was achieved for a 6.25% increase in VMTCO to 8.5 g L−1 h−1 (12.2 kgCO2-eq kg−1 IPA; Netherlands case) and a −23.2% in IPA production costs for a 30% decrease in glycerol bleed of 7 wt% (USD 3.28 per kgIPA, US case) compared with the base-case process. © 2025 The Author(s). Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

The iron and steel industry is responsible for 30% of all industrial CO2 emissions, largely emitted via hot Basic Oxygen Furnace (BOF) gas (CO, H2, CO2). Gas fermentation can convert the BOF gas into valuable chemicals such as the disinfectant and platform chemical isopropyl alcohol (IPA), which is currently only produced with petrochemical cracking. The goal of this research was to model the state-of-the-art industrial-scale BOF gas fermentation to IPA and identify the key process parameters affecting technical performance. The designed and modelled industrial-scale process was based on the published LanzaTech technology with Clostridium autoethanogenum. In the process model, the IPA is purified through extractive distillation with pure glycerol as an entrainer. During sensitivity analysis, eleven process parameters were investigated for their effect on the eighteen chosen technical Key Performance Indicators (KPIs). These process parameters are (product selectivity (YIPA/CO), CO volumetric mass transfer rate (VMTCO), CO conversion, reactor dilution rate (D), temperature off-gas condenser, biomass separation liquid loss, extractive distillation glycerol mole fraction, extractive distillation molar reflux ratio, glycerol recycle purge, broth recycle purge and anaerobic digestion waste conversion). The sensitivity analysis identified that the key technical parameters affecting the KPIs are the gas fermentation parameters (CO conversion, VMTCO, YIPA/CO, and D) as well as the biomass filtration liquid loss. Moreover, increasing CO conversion, VMTCO, YIPA/CO as well as decreasing D and the biomass filtration liquid loss all individually had the greatest positive impact on the KPIs. Thus, this study has successfully synthesised and modelled a state-of-the-art industrial-scale BOF gas fermentation to IPA process and identified the key process parameters to improve its technical process performance. These findings can be used both to optimise the BOF gas fermentation to IPA process, and perform further economic evaluations and environmental impact assessment.