Syngas fermentation to ethanol
the effects of gas recycling on economics
H. Shijaz (Eindhoven University of Technology, TU Delft - BT/Biotechnology and Society)
F. Gallucci (Eindhoven University of Technology)
Adrie J J Straathof (TU Delft - BT/Bioprocess Engineering)
John A. Posada-Duque (TU Delft - BT/Biotechnology and Society)
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Abstract
Syngas fermentation is a biochemical pathway to produce ethanol and has been commercialized successfully. The economic viability of this process could be further improved to become more competitive in the existing ethanol market. Improving gas utilization is the key, and can be done by recycling the unreacted syngas. This work is an early-stage techno-economic assessment of recycling in producing ethanol from Basic Oxygen Furnace (BOF) gas. Economic viability is measured in terms of Relative Competitive Percentage (RCP) and is a measure of closeness to the current market. Two scenarios, firstly a once-through process, and secondly a process with recycling (0.9 split ratio: recycle/purge) of gas is considered. None of them showed a positive RCP as compared to the current ethanol market. Comparing these scenarios, beyond the single pass conversion of 60%, the additional production costs due to recycling become dominating and lead to a lower RCP compared to once-through systems.