Duty Cycling Influences
Current Generation in Multi-Anode
Environmental Microbial Fuel Cells
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Abstract
Improving microbial fuel cell (MFC) performance continues
to be
the subject of research, yet the role of operating conditions, specifically
duty cycling, on MFC performance has been modestly addressed. We present
a series of studies in which we use a 15-anode environmental MFC to
explore how duty cycling (variations in the time an anode is connected)
influences cumulative charge, current, and microbial composition.
The data reveal particular switching intervals that result in the
greatest time-normalized current. When disconnection times are sufficiently
short, there is a striking decrease in current due to an increase
in the overall electrode reaction resistance. This was observed over
a number of whole cell potentials. Based on these results, we posit
that replenishment of depleted electron donors within the biofilm
and surrounding diffusion layer is necessary for maximum charge transfer,
and that proton flux may be not limiting in the highly buffered aqueous
phases that are common among environmental MFCs. Surprisingly, microbial
diversity analyses found no discernible difference in gross community
composition among duty cycling treatments, suggesting that duty cycling
itself has little or no effect. Such duty cycling experiments are
valuable in determining which factors govern performance of bioelectrochemical
systems and might also be used to optimize field-deployed systems