Bringing High-Rate, CO2-Based Microbial Electrosynthesis Closer to Practical Implementation through Improved...

Area of Science:

• Biotechnology
• Electrochemistry
• Environmental Science

Background:

• Microbial electrosynthesis (MES) offers a promising route for converting CO2 into valuable products like acetate.
• Scaling up MES technology requires optimizing operational parameters for enhanced efficiency and economic viability.

Purpose of the Study:

• To optimize key design and operating conditions for microbial electrosynthesis (MES) of acetate from CO2.
• To investigate the impact of pH, cathode potential, electrode material, and CO2 source on acetate production rates and electron recovery.

Main Methods:

• Investigated the effect of varying pH levels on acetate production rate and methanogenic activity.
• Applied different cathode potentials and measured electron recovery and current density.
• Utilized reticulated vitreous carbon electrodes with specific macropore sizes.
• Tested synthetic biogas mixtures as the CO2 source.

Main Results:

• Optimal pH for acetate production was found to be 5.2, suppressing methanogenic activity.
• A cathode potential of -1.1 V vs. SHE achieved 99% electron recovery as acetate at high current densities (~200 A m(-2)).
• Exceptional acetate production rates of up to 1330 g m(-2) day(-1) were achieved at pH 6.7.
• Macroporous electrodes (0.6 mm) balanced surface area and mass transfer effectively.
• Synthetic biogas as a CO2 source yielded comparable MES performance to pure CO2.

Conclusions:

• Optimized conditions, including pH 5.2 and specific electrode design, significantly enhance MES acetate production.
• High current densities and efficient electron recovery are achievable, supporting practical applications.
• The use of synthetic biogas demonstrates the technology's potential for biogas upgrading and CO2 valorization.