# Single Cell Protein Production From Ethanol: Model‐Based Bioreactor Operation at Industrial Scale

## TL;DR

This study models industrial-scale ethanol fermentation using pure oxygen to produce single cell protein, highlighting technical feasibility and challenges.

## Contribution

A model-based approach to assess industrial-scale ethanol fermentation for SCP using pure O2 and operational constraints.

## Key findings

- A 600 m³ fermenter could produce up to 58 kt/y of SCP with a high O2 transfer rate of 1.1 mol/(kg h).
- High dissolved CO2 and heat production may hinder biomass production despite high O2 transfer.
- The model predicts a microbial biomass yield of 0.61 gx/gethanol with further experimental validation needed.

## Abstract

Alternative fermentation feedstocks such as ethanol can be produced from CO2 via electrocatalytic processes that coproduce O2. In this study, industrial‐scale fermentation of ethanol with pure O2 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 m3 bubble column operating in continuous mode was assessed and attributed mainly to a high O2 transfer rate of 1.1 mol/(kg h) through the use of pure O2. However, most of the pure O2 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 CO2 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 gx/gethanol (> 95% Yx/smax). Although the large predicted O2 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.