Continuous Electricity Generation at High Voltages and Currents Using Stacked Microbial Fuel Cells

TLDR

Connecting several microbial fuel cell units in series or parallel can raise voltage and current, but the impact on microbial electricity generation was previously unknown. This study demonstrates a clear link between electrochemical performance and microbial composition in MFCs, supporting their potential for useful energy generation. Series connection caused individual MFC voltages to diverge due to microbial limitations at higher currents, and over time the microbial community shifted from diverse to Gram‑positive dominance. The stacked array of six continuous MFCs reached a peak hourly power of 258 W m⁻³, with series and parallel configurations boosting voltage to 2.02 V and current to 255 mA while preserving high power, and the community shift tripled short‑time power from 73 to 275 W m⁻³ and lowered internal resistance from 6.5 Ω to 3.9 Ω.

Abstract

Connecting several microbial fuel cell (MFC) units in series or parallel can increase voltage and current; the effect on the microbial electricity generation was as yet unknown. Six individual continuous MFC units in a stacked configuration produced a maximum hourly averaged power output of 258 W m-3 using a hexacyanoferrate cathode. The connection of the 6 MFC units in series and parallel enabled an increase of the voltages (2.02 V at 228 W m-3) and the currents (255 mA at 248 W m-3), while retaining high power outputs. During the connection in series, the individual MFC voltages diverged due to microbial limitations at increasing currents. With time, the initial microbial community decreased in diversity and Gram-positive species became dominant. The shift of the microbial community accompanied a tripling of the short time power output of the individual MFCs from 73 W m-3 to 275 W m-3, a decrease of the mass transfer limitations and a lowering of the MFC internal resistance from 6.5 ± 1.0 to 3.9 ± 0.5 Ω. This study demonstrates a clear relation between the electrochemical performance and the microbial composition of MFCs and further substantiates the potential to generate useful energy by means of MFCs.