Defying Gravity to Enhance Power Output and Conversion Efficiency in a Vertically Oriented Four-Electrode...

Area of Science:

• Microbial Fuel Cells (MFCs)
• Bioelectrochemistry
• Environmental Engineering

Background:

• Microfluidic MFCs face diffusion limitations impacting nutrient consumption.
• Optimizing power output and conversion efficiency are key challenges in MFC development.

Purpose of the Study:

• To investigate the effect of gravity on electroactive biofilm (EAB) growth in a novel four-electrode microfluidic MFC.
• To compare biofilm performance on upward- and downward-facing electrodes.
• To evaluate the potential for increased power density and substrate consumption in a parallel electrode configuration.

Main Methods:

• Designed and conducted long-term experiments using a four-electrode microfluidic MFC.
• Grew Geobacter sulfurreducens biofilms on opposing electrodes within the microchannel.
• Compared biofilm growth and performance under different gravitational orientations.
• Operated electrodes individually and in parallel to assess power output and acetate consumption.

Main Results:

• Slower EAB inoculation and growth were observed on the downward-facing anode, attributed to gravity.
• Rotating the device during growth promoted uniform biofilm formation and strong outputs from both electrodes.
• Individual electrode power densities reached over 4.0 W m^-2.
• Parallel operation of the four electrodes nearly doubled power density and acetate consumption.

Conclusions:

• Gravity can influence EAB colonization and performance in microfluidic MFCs.
• Device rotation during biofilm growth mitigates gravitational effects, leading to enhanced performance.
• The four-electrode parallel configuration significantly boosts MFC power output and substrate utilization efficiency.