Abstract
Alternative fermentation feedstocks such as ethanol can be produced from CO(2) via electrocatalytic processes that coproduce O(2). In this study, industrial-scale fermentation of ethanol with pure O(2) for single cell protein (SCP) production was studied using a modeling approach. This approach considered (i) microbial kinetics, (ii) gas-liquid transfer, and (iii) an exploration of potential operational constraints. The technical feasibility for producing up to 58 kt/y of SCP in a 600 m(3) bubble column operating in continuous mode was assessed and attributed mainly to a high O(2) transfer rate of 1.1 mol/(kg h) through the use of pure O(2). However, most of the pure O(2) fed to the fermenter remains unconsumed due to the large gas flows needed to maximize mass transfer. In addition, biomass production may be hampered by high dissolved CO(2) concentrations and by large heat production. The model estimates a microbial biomass concentration of 114 g/kg, with a yield on ethanol of 0.61 g(x)/g(ethanol) (> 95% Yx/smax ). Although the large predicted O(2) transfer capacity seems technically feasible, it needs further experimental validation. The model structure allows the analysis of alternative substrates in the same way as identifying the best carbon feedstock.