A Two-Stage Continuous Fermentation System for Conversion of Syngas into Ethanol

Hanno Richter, Michael E. Martin and Largus T. Angenent
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Hanno Richter: Department of Biological and Environmental Engineering, Cornell University, Riley-Robb Hall, Ithaca, NY 14853, USA
Michael E. Martin: Department of Biological and Environmental Engineering, Cornell University, Riley-Robb Hall, Ithaca, NY 14853, USA
Largus T. Angenent: Department of Biological and Environmental Engineering, Cornell University, Riley-Robb Hall, Ithaca, NY 14853, USA

Energies, 2013, vol. 6, issue 8, 1-14

Abstract: We have established a two-stage continuous fermentation process for production of ethanol from synthesis gas (syngas) with Clostridium ljungdahlii . The system consists of a 1-L continuously stirred tank reactor as a growth stage and a 4-L bubble column equipped with a cell recycle module as an ethanol production stage. Operating conditions in both stages were optimized for the respective purpose (growth in stage one and alcohol formation in stage two). The system was fed with an artificial syngas mixture, mimicking the composition of syngas derived from lignocellulosic biomass (60% CO, 35% H 2 , and 5% CO 2 ). Gas recycling was used to increase the contact area and retention time of gas in the liquid phase, improving mass transfer and metabolic rates. In stage two, the biocatalyst was maintained at high cell densities of up to 10 g DW/L. Ethanol was continuously produced at concentrations of up to 450 mM (2.1%) and ethanol production rates of up to 0.37 g/(L·h). Foam control was essential to maintain reactor stability. A stoichiometric evaluation of the optimized process revealed that the recovery of carbon and hydrogen from the provided carbon monoxide and hydrogen in the produced ethanol was 28% and 74%, respectively.

Keywords: syngas; ethanol; Clostridium ljungdahlii; mass transfer; continuous culture (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2013
References: View complete reference list from CitEc
Citations: View citations in EconPapers (15)

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