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Microbial electrosynthesis feasibility evaluation at high bicarbonate concentrations with enriched homoacetogenic
Gunda Mohanakrishna1, Ibrahim M Abu Reesh2, Karolien Vanbroekhoven3
1Department of Chemical Engineering, College of Engineering, Qatar University, PO Box 2713, Doha, Qatar; Separation & Conversion Technologies, VITO - Flemish Institute for Technological Research, Boeretang 200, 2400 Mol, Belgium.
This study developed a method for a homoacetogenic biocathode to produce acetate from carbon dioxide using high bicarbonate concentrations, achieving efficient microbial electrosynthesis (MES). The process showed optimal performance at 15 g HCO3-/L, with further increases causing inhibition.
Area of Science:
- Microbial Electrochemistry
- Biocatalysis
- Sustainable Chemistry
Background:
- Microbial electrosynthesis (MES) offers a sustainable route for chemical production from CO2.
- Acetate production via MES is crucial for various industrial applications.
- High bicarbonate concentrations pose challenges for biocathode stability and efficiency.
Purpose of the Study:
- To develop an enrichment methodology for a homoacetogenic biocathode capable of functioning at high bicarbonate concentrations.
- To optimize the microbial electrosynthesis (MES) of acetate from carbon dioxide.
- To investigate the impact of increasing bicarbonate concentrations on acetate production rate and carbon conversion efficiency.
Main Methods:
- Sequential enrichment of homoacetogenic consortia in serum bottles under increasing bicarbonate concentrations.
- Development of a biocathode using adapted biomass in a MES system.
- Monitoring of acetate production rate and carbon conversion efficiency at varying bicarbonate levels.
Main Results:
- Acetate production rate increased with bicarbonate concentration, reaching a maximum of 260 mg/L/d at 15 g HCO3-/L.
- Carbon conversion efficiency peaked at 90.16% with 2.5 g HCO3-/L, decreasing at higher concentrations.
- Biocathode development in MES showed gradual acetate production improvement, reaching 24.53 mg acetate L-1 d-1 with 47.72% carbon conversion efficiency.
- High bicarbonate concentrations (up to 20 g HCO3-/L) induced inhibition in both production rate and efficiency.
- Acetate production led to a shift in catholyte pH from neutral to acidic conditions.
Conclusions:
- The developed enrichment methodology enables homoacetogenic biocathodes to function effectively at high bicarbonate concentrations for acetate MES.
- Optimizing bicarbonate concentration is critical for balancing acetate production rate and carbon conversion efficiency.
- Further research is needed to mitigate inhibition at very high bicarbonate levels and improve MES performance compared to the enrichment stage.
