Zero-gap microbial electrolysis cells for efficient hydrogen production from real liquid waste streams.

Area of Science:

• Environmental Science
• Biotechnology
• Electrochemistry

Background:

• Zero-gap microbial electrolysis cells (MECs) achieve high performance with synthetic media.
• Application of MECs to real waste streams for biohydrogen production remains underexplored.

Purpose of the Study:

• Evaluate the performance and stability of zero-gap MECs using anaerobic digester effluent.
• Identify challenges and solutions for operating MECs with real wastewater.

Main Methods:

• Operated zero-gap MECs with single-stage anaerobic digester effluent for 30 days.
• Monitored current density and hydrogen production rates.
• Analyzed challenges such as carbonate precipitation and buffer capacity.

Main Results:

• Achieved a maximum current density of 8.8 A/m² and hydrogen production rate of 32 L/L-d.
• Sustained average performance of 7 A/m² and 20.8 L/L-d over 30 days.
• Identified carbonate precipitation as a stability issue, mitigated by acid washing; low buffer capacity limited performance.

Conclusions:

• Zero-gap MECs can effectively utilize real waste streams for biohydrogen production.
• Wastewater chemistry significantly impacts MEC performance and stability.
• Mild acid washing can address operational challenges like carbonate precipitation.