Microbial fuel cell (MFC): Novel biotechnological approach for harnessing
bioelectricity in association with wastewater treatment
S Venkata Mohan, S. Veer Raghavulu, G Mohanakrishna, S Srikanth, G
Velvizhi, R Kannaiah Goud, P. N. Sarma
Bioengineering and Environmental Center, Indian Institute of Chemical Technology,
Hyderabad-500 007, India
E-mail: vmohan_s@yahoo.com; svmohan@iict.res.in
The global energy demand increases the difficulty in sustained supply and the associated
problems of pollution and global warming are acting as a major impetus for research into
alternative renewable energy technologies. It is well known that microorganisms can
produce fuels such as ethanol, methane and hydrogen from organic matter. More
recently, it has been reported that microorganisms can also convert organic matter into
electricity using microbial fuel cell (MFC). MFC is a hybrid bio-electrochemical system,
which converts the substrate directly into electricity by the oxidation of organic matter in
the presence of bacteria (bio-catalyst) at ambient temperature/pressure. The potential
developed between the bacterial metabolic activity [reduction reaction generating
electrons (e−) and protons (H+)] and electron acceptor conditions separated by a
membrane manifests bioelectricity generation. In view of environmental sustainability,
using wastewater reduces the cost of wastewater treatment and also generates bio-energy
from microbial metabolism at the same time accomplishing treatment. Wastewaters
generated from various industrial processes can be considered as ideal substrate as they
contain high concentrations of biodegradable organic material, which results in a net
positive energy or economic balance. Exploiting wastewater as substrates to generate
electricity and feasibility to operate with mixed culture at ambient temperatures and
pressures makes this process less energy intensive and more environmental friendly.
Employing wastewaters in MFC for energy generation is in the early stages of research.
In this direction for past five years we have focused our research on the feasibility of
harnessing bioelectricity from various types of wastewater employing low-cost,
mediatorless, non-catalyzed MFC using mixed culture as anodic biocatalyst. In this
communication, we have made an attempt to consolidate work carried out in our
laboratory using various wastewater viz., chemical, domestic, dairy, market based
vegetable and molasses based distillery wastewaters as substrates using mixed consortia
[1-12]. Process is evaluated based on bioelectricity generation in concurrence with
substrate degradation. An attempt was also made to evaluate the process parameters such
as type and nature of wastewater, loading rate, retention time, nature of anodic inoculum
used (aerobic and anaerobic), pH of wastewater (acidophilic/neutral/basic), distance
between electrode, nature of electrode materials (graphite, steel, nickel, copper and
aluminum), membrane electrode assembly, electrolytes used, fuel cell configuration
(single and dual) and nature of anodic microenvironment (aerobic, anoxic and anaerobic)
on the performance of the fuel cell based on power output parameters and substrate
removal efficiency. MFC behavior was evaluated based on polarization, cell potentials,
columbic efficiency, impedance analysis, and bioprocess monitoring. Cyclic voltammetry
(CV) was done to characterize and evaluate the redox reactions occuring during the fuel
cell operation. Relative decrease in anodic potential (RDAP) with the function of applied
external resistance was also evaluated to derive the maximum sustainable power. All the
process parameters evaluated showed marked influence on both power generation and
substrate degradation. During MFC operation, there exists a possibility to integrate
diverse components (biological, physical and chemical) which provides an opportunity to
trigger multiple reactions (bio-chemical, physical, physico-chemical, electrochemical,
oxidation, etc.) cohesively termed as bio-electrochemical reactions as a result of bacterial
metabolic activity and subsequent secondary reactions resulting ins power generation and
simultaneous wastewater treatment. Our results enumerated the potentiality of MFC
technology more promising compared to conventional chemical fuel cells.
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