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 CO ₂ emissions from steel mill off gas, and including steel mill heat replacement. Parametric assessment identified higher CO volumetric mass transfer rate (VMT _CO) 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 VMT _CO. At best, a −44.4% GWP was achieved for a 6.25% increase in VMT _CO to 8.5 g L ⁻¹ h ⁻¹ (12.2 kgCO ₂-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 kg _IPA, US case) compared with the base-case process.

Steel mill off gas fermentation presents a promising green alternative to petrochemical isopropyl alcohol (isopropanol, IPA) and acetone production while potentially reducing greenhouse gas emissions. A pilot-scale study stated negative global warming potential (GWP) at 85% gas conversion and 90% product selectivity. However, industrial-scale plant design including detailed techno-economic assessment (TEA) and life cycle assessment (LCA) remain undescribed. Therefore , this study modelled a heat-integrated 47.5 kton/ year gas fermentation process to IPA and acetone, based on pilot-scale data. The downstream processing was designed using vacuum distillation and heat-pump integrated (extractive) distillation to purify the 50 gproduct/ L broth with bi-omass and acetate as byproducts, to obtain 41.8 kton/ year of 99.6 wt. % IPA and 5.64 kton/ year of 99.0 wt. % acetone. Notably, no steam is consumed and 2.6 MWh of electricity is generated by utilising the energy from the steel mill off gas. The estimated unit production cost (UPC; 0.57 /kgproduct)issignificantlybelowmarketprices(1.65/ kgIPA and 1.45 $/ kgacetone). Moreover, the cradle-to-gate LCA gave GWPs of-1.42 kgCO2-eq/ kgIPA and-1.25 kgCO2-eq/ kgacetone, mainly due to avoided steel mill emissions. Other environmental impacts studied were also lower than for petrochemical production. Only the freshwater use is higher (70 L/ kgIPA and 62 L/ kgacetone) compared to petrochemical production (16 L/ kgIPA and 28 L/ kgacetone). Future research should study the impact of IPA and acetone selectivity and titer on the economic and environmental sustainability of steel mill off gas fermentation to IPA and acetone.

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.