Page 63 - Energy from Toxic Organic Waste for Heat and Power Generation

Toxic Waste From Textile Industries 51

chemical energy to electrical energy, MFCs have many potential applica-
tions, such as electricity generation, bio-hydrogen production, wastewater
treatment, and biosensor [28].
Microorganisms oxidize substrates in the anodic chamber to produce
electrons and protons, while producing carbon dioxide as an oxidation
product. Electrons attached on anode (negative terminal) flow to the cath-
ode (positive terminal) through an external circuit. Protons migrate across
the proton/cation exchange membrane to combine with electrons to form
water if oxygen is provided or to form ferrocyanide if ferricyanide is pro-
vided. Therefore, a positive current flows from the positive terminal to the
negative terminal and this direction is opposite to electron flow [28]. This
is how MFCs generate electricity through microorganisms [28] as shown
in Fig. 4.1.
In MFCs, oxidation of organic carbon sources does not contribute net
carbon dioxide to the atmosphere, and there is no need for extensive pre-
processing of the fuel or expensive catalysts. These are the major advan-
tages of MFCs over hydrogen fuel cells; however, the power production by
MFCs is currently limited mainly due to either high internal resistance or
efficiency of the cathodic reaction, and feasibility of scale-up of MFCs is
restricted by the high cost of membranes [28].

Meter
Load
Bacteria e –
e –

Organic
compounds + O 2
as fuel H H +
H + H +
H +
+
Oxidation H H O
products H + 2
Anode Cathode

Proton exchange
membrane
Fig. 4.1 Schematic diagram of two-chamber microbial fuel cells [28].