Increasing methane content in biogas and simultaneous value added product recovery using microbial electrosynthesis

Area of Science:

• Electrochemistry
• Biotechnology
• Environmental Science

Background:

• Biogas purification is crucial for sustainable energy.
• Carbon dioxide (CO2) in biogas presents an opportunity for valorization.
• Microbial electrosynthesis (MES) is an emerging technology for CO2 conversion.

Purpose of the Study:

• To investigate the electrosynthesis of multi-carbon compounds from CO2 in biogas.
• To optimize MES parameters for enhanced product yield and energy efficiency.
• To identify optimal electrode and electrolyte combinations for biogas upgrading.

Main Methods:

• Fabrication of MES cells with various electrode materials.
• Operation of MES cells using different electrolytes and mixed anaerobic cultures.
• Application of a cathode potential of -0.7 V vs standard hydrogen electrode (SHE).

Main Results:

• Production of acetate (0.81 mM/day), isobutyrate (0.63 mM/day), propionate (0.44 mM/day), and 2-piperidinone (0.53 mM/day) from CO2 reduction.
• Traces of methyl derivatives detected due to methane presence in biogas.
• Optimal conditions identified: nickel foam anode, 1 M NiSO4 anolyte, graphite felt cathode, pH 5.2 phosphate buffer catholyte.

Conclusions:

• MES is a viable method for biogas purification and CO2 valorization.
• Specific electrode and electrolyte combinations significantly impact MES performance.
• Optimized MES offers enhanced product yield and energy efficiency for biogas upgrading.