Microbial fuel cells (MFCs) provide

Microbial fuel cells (MFCs) provide new opportunities to produce
energy from biodegradable wastes, providing a sustainable
system for energy production and waste valorization [1–5]. The
concept requires microorganisms able to transfer electrons exogenously
and uses electrodes as final electron acceptors [6]. A MFC
consists of two compartments, anodic and cathodic, separated by
an ion exchange membrane. The microorganisms in the anodic
compartment oxidize the substrates, producing electrons that are
transferred to the cathode through an external circuit, whereas the
produced protons are transferred by the ion exchange membrane.
In the cathode the electrons and protons combine with a chemical
catholyte such as oxygen. This concept is schematically represented
in Fig. 1.
The first evidence that some microorganisms can generate electricity
was reported by Potter in 1911 [7]. However, the exponential
increase in MFC research was only observed in the last two decades,
with the discovery that microorganisms can self mediate the transport
of electrons to the electrodes. The most studied potential
application for MFCs is on energy efficient wastewater treatment
[4,8,9]. Currently, several variations of MFC concepts exist in the
∗ Corresponding author. Tel.: +351 210924600x4200; fax: +351 217163636.
E-mail address: cristina.matos@lneg.pt (C.T. Matos).
literature, such as: micro electrolyses cells [5], live plant microbial
fuel cells [10],