Volumetric mass transfer and dilution rate as key parameters for sustainable industrial syngas fermentation to isopropyl alcohol: modeling and parametric assessment
G.J.A. Brouwer (TU Delft - BT/Biotechnology and Society)
M.J. George Lourdusamy (Student TU Delft)
M.B. Meijer-Jansen (TU Delft - Group Sinke)
John A. Posada
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Abstract
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.
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