Abstract
Decarbonisation of the economy has become a priority at the global level, and the resulting legislative pressure is pushing the chemical and energy industries away from fossil fuels. Microbial electrosynthesis (MES) has emerged as a promising technology to promote this transition, which will further benefit from the decreasing cost of renewable energy. However, several technological challenges need to be addressed before the MES technology can reach its maturity. The aim of this review is to critically discuss the bottlenecks hampering the industrial adoption of MES, considering the whole production process (from the CO2 source to the marketable products), and indicate future directions. A flexible stack design, with flat or tubular MES modules and direct CO2 supply, is required for site-specific decentralised applications. The experience gained for scaling-up electrochemical cells (e.g. electrolysers) can serve as a guideline for realising pilot MES stacks to be technologically and economically evaluated in industrially relevant conditions. Maximising CO2 abatement rate by targeting high-rate production of acetate can promote adoption of MES technology in the short term. However, the development of a replicable and robust strategy for production and in-line extraction of higher-value products (e.g. caproic acid and hexanol) at the cathode, and meaningful exploitation of the currently overlooked anodic reactions, can further boost MES cost-effectiveness. Furthermore, the use of energy storage and smart electronics can alleviate the fluctuations of renewable energy supply. Despite the unresolved challenges, the flexible MES technology can be applied to decarbonise flue gas from different sources, to upgrade industrial and wastewater treatment plants, and to produce a wide array of green and sustainable chemicals. The combination of these benefits can support the industrial adoption of MES over competing technologies.
Highlights
Climate change has become one of the most challenging issues faced by humanity
carbon capture and utilization (CCU) technologies will mitigate greenhouse gas (GHG) emissions both directly, by capturing CO2 that would be otherwise released to the atmosphere, and indirectly, by displacing fossil fuel-based chemicals and fuels currently used by industries with green alternatives
At pH 4, instead, the rejection drastically decreased, since the separation becomes mostly steric for undissociated acids, showing the possibility to achieve selective separation
Summary
Climate change has become one of the most challenging issues faced by humanity. After signing the Paris agreement in 2015, most countries worldwide committed to decreasing their greenhouse gas (GHG) emissions to contain global warming to 2°C (above pre-industrial levels), aiming to 1.5°C by 2050 (United Nations, 2015). The European Union (EU) set a target of 20% GHG reduction by 2020, 40% by 2030 and of achieving a net-zero carbon economy by 2050. Significant efforts and innovative measures need to be developed to achieve the ambitious target of net-zero carbon emissions by 2050 Such efforts were translated into the European. CCU technologies will mitigate GHG emissions both directly, by capturing CO2 that would be otherwise released to the atmosphere, and indirectly, by displacing fossil fuel-based chemicals and fuels currently used by industries with green alternatives. Microbial electrosynthesis (MES) is a promising CCU technology for bio-electro CO2 recycling into valuable chemical products, including organic acids (Batlle-Vilanova et al., 2017; Jourdin et al, 2015), alcohols (Arends et al, 2017; Gavilanes et al, 2019; Vassilev et al, 2019), and bioplastics (Pepè Sciarria et al, 2018). Future directions were suggested, based on previous experience on similar technologies, for putting forward resilient and sustainable CO2 recycling MES biorefineries
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