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.
To date, many organic substrates have been
investigated as possible energy sources to generate electricityusing MFCs. Below, an overview is given of the substrates which have been used to fuel MFCs.
If bacteria want to survive, grow or become dominant
within a microbial community, they do not only require
substrate and nutrients but they also need the presence of an appropriate
electron acceptor. Based on the usage of a final electron acceptor, there are two main modes of microbial
energy conservation: respiration and fermentation. These processes are
ubiquitous in various natural environments.
Recently, they have been accompanied
by a new exciting respiration process occurring in bioelectrochemical systems
(BESs): electrogenesis.
The working principles of these three processes are covered in this item.
The microbial conversion of substrates is a key process to generate
electricity in BESs. Despite, the microbial nature of the process, it is
affected by electrochemical laws and principles which generally results in a
lowering of the attainable voltage. The main electrical principles and the
processes governing these losses are briefly described. Subsequently, the various
conversions efficiencies are discussed.
Principles 
