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A microbial fuel cell (MFC) converts
chemical energy, available in
a bio-convertible substrate, directly into electricity.
To achieve this, bacteria are used as a catalyst to convert
substrate into electrons.
Bacteria are very small (size
appr. 1 µm) organisms which can convert a huge variety of
organic compounds into CO2, water and energy. The
micro-organsisms use the produced energy to grow and to maintain
there metabolism. However, by using a MFC we can harvest a part
of this microbial energy in the form of electricity.
A MFC consists of an anode,
a cathode, a proton or cation exchange membrane
and an electrical circuit.
A General layout of a MFC in
which in the anodic compartment the bacteria can bring about
oxidative conversions while in the cathodic compartment
chemical and microbial reductive processes can occur. (After
Rabaey & Verstraete, 2005)
The bacteria live in the
anode and convert a substrate such as glucose, acetate
but also waste water into CO2, protons and electrons.
Under aerobic conditions, bacteria use oxygen or nitrate as a
final electron acceptor to produce water. However, in the anode
of a MFC, no oxygen is present and bacteria need to switch from their natural electron
acceptor to an insoluble acceptor,
such as the MFC anode. Due to the ability of bacteria to
transfer electrons to an insoluble electron acceptor, we can use
a MFC to collect the electrons originating from the microbial
metabolism. The electron transfer can occur either
via membrane-associated components, soluble electron
shuttles or nano-wires.
The electrons then flow through an
electrical circuit with a load or a resistor to the cathode.
The potential difference (Volt) between the anode and the
cathode, together with the flow of electrons (Ampere) results in
the generation of electrical power (Watt).
The protons flow through the
proton or cation exchange membrane to the cathode.
At the cathode, an electron acceptor is
chemically reduced. Idealy, oxygen is reduced to water. To
obtain a sufficient oxygen reduction reaction (ORR) rate a
Platina-catalyst has to be used. However, many researchers have
tried to used other non-noble metal catalysts.
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Principles 
