Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 3, Pages: 915-924  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link: http://www.jett.dormaj.com  
Microbial Fuel Cell: An Emerging Technology for  
Wastewater Treatment and Energy Generation  
1*  
1
Karan Singh and Dharmendra  
Department of Civil Engineering, National Institute of Technology, Hamirpur, (H.P.), India - 177005  
Received: 13/02/2020 Accepted: 07/04/2020 Published: 20/05/2020  
Abstract  
Microbial fuel cells (MFCs) are enticing surprising attention due to their dual functions of energy generation and waste removal  
from wastewaters. Microbial fuel cells use microbial metabolism to convert biochemical metabolic energy into electrical current by  
using different substrates. Microbes are fed in the anode with the substrate (e.g., domestic, industrial, leachates, etc.) to enhance the  
performance of microbial fuel cells. It provides an opportunity for the feasible production of energy from bio-degradable organic matters  
while treating wastewater. In recent years, despite the extensive efforts to improve the efficiency of the cell, energy production is still  
low, especially in scaled-up systems. However, the construction cost of microbial fuel cells is relatively higher than fossil fuel prices, so  
it makes doubtful that power generation can ever be competitive with existent energy generation approaches but improvements in power  
densities, reductions in materials costs may make microbial fuel cells real-world for electricity generation. In-depth review of literature,  
the study summarizes the role of microorganisms and substrate in the anode chamber. It includes types, components, mechanism and  
operation of microbial fuel cells. This review highlights various parameters affecting microbial fuel cells, current challenges and  
applications in the production of electrical energy in a sustainable way.  
Keywords: Biodegradable; Metabolic energy; Microbial fuel cell; Nutrient removal; Wastewater treatment  
Introduction1  
architectures for maximizing the columbic efficiency and  
1
power generation is the main challenge for an MFC. Further  
challenges coming in the way are to reduce the cost and make  
architecture for MFC that are intrinsically scalable (25-28).  
This study highlights different factors affecting the  
performance of MFC, its benefits, limitations, and role of  
substrates and microorganisms.  
The demand for renewable energy will possibly comprise a  
huge portion of global energy production and their usage in the  
future (1-2). Present prospects for global energy have been  
direct us to move towards non-renewable energy (3-4). Now a  
day; non-renewable resources of energy are exhausting at a  
much faster rate which suggests the development of different  
cost-effective renewable energy technologies. India has  
abundant sources of renewable energy, biomass (organic  
matters) is one of them (5). The total available volume for  
electricity generation in India was about 2670 GW till 2013 in  
which the contribution of renewable energy was 10.5%.  
Biomass contributes 12.83% of total renewable energy  
generation (6). Hence, a lot of biomass (substrate) is available,  
which has a high potential to generate energy with the help of  
microbial fuel cell (MFC). The MFC is one of the technologies  
with the potential for promoting self-sustainability and  
resource efficiency in the treatment of wastewater (7-12). MFC  
comprises anode and cathode compartment. The  
proton/cation/anion membrane or salt bridge divides the anodic  
and cathodic compartments. Anode creates biofilm at its  
surface which acts as a catalyzer to transform biochemical  
energy into electrons, while the oxygen acts as an electron  
acceptor to form water at the cathode (13-15). MFC has the  
capability to transform biochemical energy which is present in  
waste biological matter into electrical energy with bacterial  
2 Classification of microbial fuel cells (MFC)  
The classification of MFC is essential because it states  
about the efficiency of MFC, i.e. coulombic efficiency,  
permanency, robustness, and power output. The design which  
produces high power and coulombic efficiency based on cost-  
effective materials are required for practical applications,  
which can be implemented on a large scale (25). There are a  
number of designs for the manufacturing of an MFC depending  
upon different chambers, type of operation, etc. Some  
principally include the following types of MFC.  
2.1 Single chamber MFC  
A modest and more competent MFC can be prepared by  
neglecting the cathode compartment and inserting the cathode  
electrode directly into the PEM (Proton exchange membrane).  
Single chamber MFC contains both the anode and the cathode  
in a single compartment. Single chamber microbial fuel cells  
(SCMFCs) are supposed to be superior for their simple design,  
flexibility, low internal resistance, and relatively low cost.  
There is no need for oxygen in air-cathode MFC because  
oxygen is directly transferred to the cathode. The cathode  
electrode is covered with the membrane in single chambered  
catalysis (16-20). Currently, MFC is considered as  
a
sustainable technology for the generation of energy (21-24).  
Material selection is important because it affects the efficiency  
of MFC in terms of microbial growth and efficiency of  
reactions involved. Finding the best suitable materials and  
Corresponding author: Karan Singh, Department of Civil  
Engineering, National Institute of Technology, Hamirpur,  
(H.P.), India – 177005. Email: karans72@gmail.com.  
9
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Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 3, Pages: 915-924  
MFC (29-32). Cathode electrode kept open in the Air-cathode  
single chamber MFC as shown in fig. 1 (c).  
(a)  
(b)  
(c)  
(d)  
Figure 1: Schematic diagram of (a) Dual chamber MFC (b) Up-flow MFC (c) Single chambered Air-cathode MFC (d) Stacked MFC  
2
.2 Dual chamber MFC  
Generally, batch mode study is conducted for dual  
2.4 Stacked MFC  
chambered MFCs to generate electricity and waste reduction.  
It is most widely used in laboratory scale. A typical dual  
chamber MFC consists of an anodic compartment and a  
cathodic compartment connected with the help of membrane or  
salt bridge as shown in Fig. 1(a). In the anode chamber,  
microorganism decomposes organic matter and produces free  
An assembly of MFCs in series or parallel connection  
associated with each other is as shown in Fig. 1(d) (8). MFC  
can be stacked by attaining unlike configurations of both anode  
and cathode electrodes as well as organic flow. It can be  
classified in four categories i.e., Series electrodes in parallel  
organic flow mode, Series electrodes in series flow mode,  
Parallel electrodes in parallel flow mode and Parallel electrodes  
in series flow mode (36). The parallel connected stack MFC has  
higher electrochemical reaction rate than in series. So, parallel  
connection is preferred over a series to achieve maximum COD  
removal (48). Some researchers varied anode, cathode  
electrodes, catalyst and mediators with microbial fuel cells as  
shown in Table 1.  
+
electrons and hydrogen ions. Protons (H ) are allowed by a  
membrane to move towards the cathode and at the same time  
electrons are transferred via external circuit (33-35). Free  
electrons and hydrogen ion form water in the presence of  
oxygen in the cathode chamber.  
2
.3 Up-flow MFC  
The cylindrical MFC comprises of the anode in the bottom  
of the MFC and the cathode at the top separated by glass layers  
separators) or glass wool as in Fig. 1(b). The substrate is fed  
3
Electron transfer mechanisms  
Two leading mechanisms are conveyed for the electron  
(
from the bottom to the anode compartment that passes upside  
of the cathode and exits at the top. For proper operation of the  
MFCs, a gradient is provided by transmission barrier among  
the electrodes. There is no separate anolyte and catholyte  
provided (8).  
transfers from the biological matter to the anion electrode in the  
MFC i.e., direct electron transfer and mediated electron  
transfer. Bacteria are well-known medium to the electron  
transfer to anode surface through electron shuttling with self-  
generated mediators like pycocyanin formed by Pseudomonas  
9
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Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 3, Pages: 915-924  
aerginosa (25, 49). Some bacteria needs external mediators to  
generate electricity i.e. Shewanella onedensis, Geothrix  
fermentans, etc.  
Table 1: Various types of implementation with microbial fuel cells  
COD  
removal  
Energy  
generation  
Type of MFC  
Wastewater  
Anode  
Cathode  
References  
Graphite fiber  
brushes with a  
titanium wire core  
Graphite rods  
Graphite rod  
wrapped with a  
stainless steel  
mesh marine  
grade  
Wet-proofed  
carbon cloth  
MFC-AFMBR  
MAC-MFC  
Domestic  
Domestic  
92.5%  
80%  
0.0197 kWh/m3  
-
37  
38  
Carbon cloth  
Graphite rod  
2
wrapped with a  
stainless steel mesh  
marine grade  
219 mA/m  
39 mW/m  
HUSB-CW-MFC  
Domestic  
Domestic  
61%  
39  
2
Noncatalyzed  
graphite discs  
Noncatalyzed  
graphite discs  
FME-MFCs  
>71%  
80.08 mW/m2  
621.13 mW/m2  
40  
41  
Catalyst- and  
mediator-less  
membrane  
microbial fuel cell  
Earthen pot MFC  
Dairy industry  
Rice industry  
Graphite plate  
Stainless steel  
Graphite plate  
Graphite plate  
90.46%  
96.5%  
81%  
2.3 W/m3  
42  
43  
Granular graphite Granular graphite  
Swine industry around 3 graphite around 3 graphite  
Alum sludge  
ebased CW-MFC  
0.268 W/m3  
rod  
rod  
Upflow microbial  
fuel cell  
Activated carbon  
fiber felt  
Activated carbon  
fiber felt  
carbon fiber cloth  
containing  
MnO2 catalyst  
Carbon rod  
Graphite rod  
Sea  
95%  
105 mW/m2  
44  
45  
Swine  
wastewater  
Stacked MFC  
graphite felt  
83.8%  
175W/m2  
337 W/m3  
Cross-linked MFC Domestic  
ML-MFC Domestic  
Carbon rod  
Graphite rod  
82%  
88%  
46  
47  
2
10.13mW/m  
Some chemical mediators were added to MFCs to transfer  
electrons by micro-organisms like yeast, glucose, acetate, etc.  
The direct electron transfer mechanism: It indicates direct  
transfer of electrons in between microbes and cathode electrode  
in the MFC. In this biofilm is created at the surface of anode  
electrodes through which electron transfer takes place and it  
generates additional energy in the process (50). An  
electrochemical reaction occurs at the anode when electrons  
reach to electrode surface which liberates electrons into anode.  
Direct electron transfer process takes place in the presence of  
outer membrane. Shewanella putrefaciens, Geobacter  
sulferreducens, Rhodoferax ferrireducens etc. are examples of  
direct electron transfer mechanism. Indirect electron transfer  
mechanism: In this type of mechanism, an external mediator is  
required to transfer the electrons to the cathode which may be  
generated by microbes or externally added.  
It takes place in the presence of soluble shuttles. Electron  
shuttles act as electron carrier which transfers electrons from  
microbes to the surface of electrode. The essential and optional  
components of MFC shown in Fig. 2. In the anode  
compartment, the anaerobic reactions occur which results in  
-
conversion of biological matter into electrons (e ) and hydrogen  
+
ions (H ). Electrons (e-) are transferred to the cathode via an  
external circuit and hydrogen ions (H+) are passed to the  
cathode compartment through a membrane. In cathode  
+
-
compartment hydrogen ions (H ) and electrons (e ) combine  
with oxygen which acts as an electron acceptor to form water.  
For specimen, if glucose (C  
6
H
12  
O
6
) is used as anolyte in anode  
and oxygen (O  
occur in MFC.  
2
) as an electron acceptor, Eqs. 1 and 2 reactions  
-
+
At Anode: C  
6
H
12  
O
6
+ H  
2
O → 6CO  
2
+ 24e + 24H  
(1)  
(2)  
-
+
At Cathode: O  
2
+ 4e + 4H → 2H  
2
O
4
Role of microorganisms in MFC  
A vast variety of the bacteria are available, having the  
capability of oxidizing the organic compounds and transferring  
the electrons towards anode. For the decomposition of the  
organic matter from the electrode potential, Microbial Fuel  
Cell (MFC) makes use of both types of bacterial cultures i.e.,  
pure culture and mix culture. The benefit of mixed cultures over  
the pure bacterial culture is its high substrate consumption,  
great resistance against process disturbance and consists of  
higher power based output (51). Many such types of  
microorganisms have been found and reported which are self-  
mediated i.e., which by themselves transfer the electrons across  
the membrane from anode to cathode. These microorganisms  
comprise of high columbic efficiency and are stable in nature.  
These microorganisms form a thin film on the surface of the  
Figure 2: Components of microbial fuel cell  
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Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 3, Pages: 915-924  
anode and directly transfers electrons across the membrane to  
the electrode. The names of some such effective  
microorganisms are Actinobacillus succinogenes (52),  
Aeromonas hydrophila (53), Clostridium butyricum (54),  
Escherichia coli (55), Shewanella putrefaciens (56),  
there may be over or underestimation of the information.  
Hence, because of non-standardization, the component  
dimensions and reactor information is not fully stimulated.  
Performance depends upon two important aspects, one is how  
much it produces voltages and other is the efficiency of  
treatment of the substrate. The efficiency of MFC depends on  
several factors like biological, chemical and physical  
parameters. Here some key parameters in Table 3 that describe  
the performance of MFC.  
Geobacteraceae  
sulferreducens  
(57),  
Geobacter  
metallireducens (58) and Rhodoferax ferrireducens (50) etc.  
Being self-mediated, these bacteria have reduced the use of  
mediators, has played a major role in bringing the revolution in  
the study. The cathode enhances the generation of the  
electricity and acts as the cell electron donor. In the cell,  
mediators play a major role to behave as a shuttle between  
electron carriers and anode. Some of the commonly known  
Table 2: Different researchers used microbes and synthetic  
substrate in MFC  
Synthetic  
+
Micro-organisms  
References  
mediators are neutral red, humic acid, methylene blue, Mn4  
substrate  
Glucose,  
lactose  
and Fe (III)-EDTA (52, 55, 59). Because of having a larger  
variety of substrates, mixed cultures is preferred most of the  
time for the treatment of wastewater and electricity generation.  
An array of substrates used in the blend of andophiles and  
electrophiles is proposed to be used to generate electricity from  
wastewater. Microbes enhance the reaction rate in the anode. It  
also increases the performance of MFC. It acts as a catalyst in  
the anode compartment with substrate and anolyte. Some of the  
microbes are tabulated in Table 2.  
Clostridium butyricum  
54  
Aeromonas hydrophila  
Actinobacillus  
succinogenes  
Desulfovibrio  
desulfuricans  
Acetate  
53  
52  
Glucose  
Sucrose  
59  
Glucose,  
Sucrose  
Escherichia coli  
55, 59  
Geobacter  
5
Parameters measuring the performance of  
metallireducens,  
Geobacter  
sulfurreducens,  
Rhodoferax ferrireducens  
Erwinia dissolven,  
Lactobacillus plantarum,  
Streptococcus lactis  
Pseudomonas aeruginosa  
Glucose,  
Acetate  
50, 58  
MFCs  
While talking about the performance of MFC, the two  
facets it covers are; its efficiency/capability of producing the  
power and second, the efficiency with which a given feedstock  
can be treated. Measuring the power of MFC is easy and  
straightforward, but a presentation of its data report to the  
research community is typical, creating confusion to the  
readers. Considering the different operating conditions in  
which the researchers operate and different compartment  
materials available, some of the standards are required to be  
universally accepted. For instance, the power density to opt as  
standard output for measuring the power of MFC widely.  
However, many other factors like size of cathode and anode or  
membrane are responsible for normalizing it (60). The power  
density can also be expressed in the terms of cathodic, anodic  
or liquid volumes (61). However, according to many  
researchers, some standard is required, to be universally  
accepted in this context. The reason behind this is that due to  
the lagging of such parameter, the reporting output is available  
in various formats. Due to numerous parameters involvement,  
Glucose  
Glucose  
62  
49  
Glucose,  
Lactate  
Lactate  
Shewanella putrefaciens  
Shewanella oneidensis  
56  
63  
6 Factors affecting MFC  
To improve the efficiency and lowering overall design cost  
of MFC, several factors need to be highlighted.  
6.1 Anode and cathode materials  
The efficiency of MFC may be improved in terms of power  
output, operation, and durability of the electrode.  
Table 3: Key parameters for MFC performance (25)  
Formula  
Parameters  
Unit  
RT  
cell= E°- nF 퐼푛(훱)  
p
Electrode  
Potential  
Volts  
E
r
Π= (Product) /(reactant)  
Open circuit voltage  
Current  
Power  
Volts  
OCV (open circuit voltage), Voltage obtained with indefinite resistance  
I=V/Rex  
P=I.V  
Ampere  
Watt  
2
Current density  
A/m  
j= I/A,  
2
A= Electrode surface area (m )  
Power density  
W/m2  
D