Chemicals and energy from carbon dioxide
Carbon capture and storage can provide significant emission reductions in some sectors, but has shortcomings. It has a high investment cost while the potential storage capacity is uncertain. Public resistance has also increased over the years and the process is energy-intensive. Rather than treating the captured CO2 as waste, it can be regarded as a chemical feedstock for the synthesis of other chemicals. This was the focus of the EU-funded project MICROBIOELECTROSYN (Microbially catalysed electricity driven bioproduction from CO2 at the cathode in bioelectrochemical systems). MICROBIOELECTROSYN was motivated by the recent development of bioelectrochemical systems (BESs). In particular, microbial fuel cells that use bacteria to oxidise organic and inorganic matter to generate electric current are slowly moving from the laboratory bench out to the marketplace. Several advantages, including the possibility of producing multicarbon compounds, make this bioproduction approach promising. In addition, the energy needed for electricity-driven production of fine chemicals using microorganisms can be retrieved from renewable sources. Before the MICROBIOELECTROSYN project, only a few microbial catalysts suitable for these processes had been identified. Moreover, the impact of electrode materials and other operational parameters on microbial colonisation at cathodes was not known. As a first step, the researchers developed an efficient approach for enriching a mixed but reproducible microbial community. The enriched microbial population was then successfully used in BES cathodes for the instant start-up of acetate bioproduction from CO2. The enrichment process comprised of the addition of 2-bromoethanesulfonate once in the initial phase, followed by several culture transfers in quick succession. Combined with the continuous galvanostatic operation of the cathodes, it led to the highest acetate production rates achieved so far. The successful demonstration of continuous microbial electrosynthesis opens up the way for fast conversion of CO2 and excess electrical energy into storable chemicals in the framework of the carbon capture and utilisation concept. Still, several operational parameters need to be optimised to bring this concept into practice.
Keywords
Carbon dioxide, geological storage, renewable, acetate, carbon capture and utilisation
