Decarbonizing ethanol production via gas fermentation: Impact of the CO/H2/CO2 mix source on greenhouse gas emissions and production costs

Eduardo Almeida Benalcázar,Henk Noorman,Rubens Maciel Filho,John A Posada

doi:10.1016/j.compchemeng.2022.107670

Eduardo Almeida Benalcázar, Henk Noorman + Show 2 more

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https://doi.org/10.1016/j.compchemeng.2022.107670

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Abstract

This study explores key success factors for ethanol production via fermentation of gas streams, by assessing the effects of eight process variables driving the fermentation performance on the production costs and greenhouse gas emissions. Three fermentation feedstocks are assessed: off-gases from the steel industry, lignocellulosic biomass-derived syngas and a mixture of H2 and CO2. The analysis is done through a sequence of (i) sensitivity analyses based on stochastic simulations and (ii) multi-objective optimizations. In economic terms, the use of steel off-gas leads to the best performance and the highest robustness to low mass transfer coefficients, low microbial tolerance to ethanol, acetic-acid co-production and to dilution of the gas feed with CO2, due to the relatively high temperature at which the gas feedstock is available. The ethanol produced from the three feedstocks lead to lower greenhouse gas emissions than fossil-based gasoline and compete with first and second generation ethanol.

Highlights

Global policy efforts aiming to reduce the anthropogenic emissions of greenhouse gases (GHG) and to guarantee the security of energy supply converge into the need for progressive replacement of fossil-based fuels by low-carbon and renewable fuels (COPUNFCCC, 2016; Edenhofer et al, 2014), such as ethanol
This section starts with a description of the general distributions of the global warming potential (GWP), the ethanol production costs (EPC) and the CO2 abatement costs (CAC) obtained from the stochastic simulations of the three proposed process configurations
The fermentation of the steel manufacturing off-gas is the most economically robust process configuration of the three options analyzed over the main current technological limitations of the gas fermentation stage i.e., low tolerance to ethanol, co-production of acetic acid and low mass transfer rates

Summary

Introduction

Global policy efforts aiming to reduce the anthropogenic emissions of greenhouse gases (GHG) and to guarantee the security of energy supply converge into the need for progressive replacement of fossil-based fuels by low-carbon and renewable fuels (COPUNFCCC, 2016; Edenhofer et al, 2014), such as ethanol. Syngas can be used for the production of bulk chemicals and fuels through fermentation (Almeida Benalcázar et al, 2017; Sun et al, 2019). Such process exploits the ability of acetogenic bacteria to retrieve the energy contained in CO and H2 while fixing the carbon from CO and CO2. Since acetogens are able to catabolize the components of syngas in a wide range of compositions (Abubackar et al, 2015; Leang et al, 2013), industry and academia have contemplated other sources of fermentable CO, H2 and CO2 e.g., industrial off-gases from steel manufacturing (Simpson et al, 2012) and gas mixtures containing H2 derived from the electrolysis of water (Simpson et al, 2017) and CO2 derived from the combustion of carbonaceous materials

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