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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 9, Issue 9, September 2018, pp. 137–148, Article ID: IJMET_09_09_017
Available online at http://iaeme.com/Home/issue/IJMET?Volume=9&Issue=9
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
FACTORS AFFECTING THE PERFORMANCE
OF MICROBIAL FUEL CELLS
Shanmuganathan. P* and Rajasulochana. P
Corresponding Author*, Bharath University, Agaram main road, Selaiyur, Chennai
Ramachandra Murthy. A
CSIR-Structural Engineering Research Centre, CSIR Road, Taramani, Chennai
ABSTRACT
A microbial fuel cell (MFC) is a bioreactor presents an advanced eco-friendly
technology that converts chemical energy in the chemical bonds in organic
compounds to electrical energy through catalytic reactions of microorganisms under
anaerobic conditions. It has been known for many years that it is possible to generate
electricity directly by using bacteria to break down organic substrates. The recent
energy crisis has invigorated interests in MFCs among educational researchers as
some way to generate electrical power or hydrogen from biomass without a net
carbon emission into the ecosystem. MFCs may be utilized in waste product treatment
facilities to break down organic matters. MFCs can also be used in wastewater
treatment facilities to organic matters. It was also studied for applications as
biosensors for biological oxygen demand monitoring. Power output and Coulombic
efficiency are found to be significantly affected by the types of microbe in the anodic
chamber of an MFC, configuration of the MFC and operating conditions. Presently,
real-world applications of MFCs are limited because of their low power density level
2
of several thousand mW/m . This paper presents a review on factors affecting
performance of microbial fuel cells.
Keywords: MFC, Electrode materials, Bio cathodes
Cite this Article: Shanmuganathan. P, Ramachandra Murthy. A and Rajasulochana.
P, Factors Affecting the Performance of Microbial Fuel Cells, International Journal of
Mechanical Engineering and Technology, 9(9), 2018, pp. 137–148.
http://iaeme.com/Home/issue/IJMET?Volume=9&Issue=9
1. INTRODUCTION
Microbial fuel cell (MFC) is a novel technology which will be used for electricity generation
during oxidization of the organic substances presented in the substrate. To obtain a desirable
performance, it is essential to understand the influential factors on the MFC. Among the
numerous factors affecting the MFC performance, (i) substrate, (ii) microorganisms and their
metabolism, (iii) electron transfer mechanism in an anodic chamber, (iv) electrodes material
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Factors Affecting the Performance of Microbial Fuel Cells
and the shape of electrodes, (v) type of membrane, (vi) operating conditions such as
temperature, pH and salinity, electron acceptor in a cathodic chamber and (vii) geometric
design of the MFC are considered as the most important factors. Among different substrates,
wastewater is a sustainable rich medium which can be treated by MFCs. There are various
types of exoelectrogenic bacteria presented in wastewaters which can oxidize organic matter
and transfer electrons to the anode without using mediators. Like other microbial systems,
optimum pH and temperature enhance the bacterial growth which can improve the MFC
performance. Despite the negative effect of salt on microbial growth, higher salinity and ionic
strength can increase the conductivity of substrate and therefore enhance MFC performance.
Scaling up MFC is a controversial issue which needs a comprehensive understanding of these
factors. By using new inexpensive materials for electrodes and membrane for manufacturing
MFCs, a more cost-effective design for scalable wastewater treatment and high power
generation can be achieved. Furthermore, MFC is a suitable candidate for bioremediation of
contaminated groundwater.
Electrode design is the greatest challenge in making MFC a cost effective and scalable
technology. Recently, interest in the electrode material and its configuration has steadily
increased in studies for MFC. Over the past decade, a variety of electrodes have been
extensively explored for MFC. These electrodes can be classified into two main groups, bio-
electrodes (including anode and bio cathode) and chemical-electrodes (more specifically, air–
cathode and aqueous air–cathode), according to whether or not bacteria is used as a catalyst.
A typical MFC consists of two chambers that are separated by a proton exchange membrane
(PEM) in which the anodic chamber is anaerobic and the cathodic chamber is aerobic [Du et
al., 2007]. As a substrate, the wastewater can be treated in the anodic chamber and besides
that the electricity will be generated [Oh et al., 2010; Du et al., 2007; Mohan et al., 2008]. In
some cases, bio cathodes were used in order to treat wastewater aerobically [Xia et al., 2013].
By removing oxygen from the cathodic chamber and applying a small additional voltage to
the circuit, hydrogen gas is evolved from the cathode. This kind of biological fuel cell is
called Bio-Electrochemically Assisted Microbial Reactor [Liu et al., 2005; Logan and Regan,
2006]. Very recently, a new type of bio electrochemical systems called microbial desalination
cell (MDC) was developed by keeping two membranes between the anode and the cathode in
MFC [Cao et al., 2009; Luo et al., 2012; Jacobson et al., 2011]. Desalination efficiency using
MDCs is limited by the voltage produced by the bacteria. In some cases, microbial
electrodialysis cell was developed to concurrently desalinate saline waters and produce
hydrogen gas [Lou et al., 2011]. Using MDCs, wastewater treatment, electricity production
and water desalination is possible simultaneously [Qu et al., 2012; Kim and Logan, 2012].
This paper reviews the factors affecting the performance of MFCs towards power
generation.
2. FACTORS AFFECTING THE PERFORMANCE OF MFCS
There are several factors that affect the performance of MFCs and its energy production in
wastewater treatment. In order to have a highly efficient MFC, recognizing and considering
these factors are essential. Microorganisms in the anodic chamber are important due to their
metabolism and the mediators which are used by them for transferring electron to the anode.
There are various substrates which can be used as the source of electron donors in the MFC
and oxidized by microorganisms. Operating conditions such as pH, temperature, ionic
strength of the mediums, material and construction of the anode, cathode and membrane could
have a considerable impact on electricity generation. Figure 1 shows a summary of these
factors.
http://iaeme.com/Home/journal/IJMET 138 editor@iaeme.com
Shanmuganathan. P, Ramachandra Murthy. A and Rajasulochana. P
Figure 1 Factors affecting the performance of MFCs
2.1. Electron transfer mechanism
Electrons that are produced in the anodic chamber should be transferred to the anode by
shuttles or electron mediators. Some microorganisms, such as Saccharomyces species and E.
coli used in some MFCs, have an outer layer of non-conductive lipid membrane, including
peptidoglycans and lipopolysaccharides that slowdown the direct electron transfer to the
anode. The mediatorsare typically dyes such as methylene blue, neutralred, thionine, methyl
viologen or humic acid.
2.2. Microbial metabolism and cell potential
Microorganism metabolic pathway and the consequent potential of the anode is the main
parameter in determining the cell potential. Bacterial catabolism is the rate limiting step in
MFCs. Heterotrophic organisms gain their energy from oxidation of organic compounds. Due
to the involvement of exogenous oxidants, that is, external terminal electron acceptors, two
major metabolic pathway staking place in the anodic chamber are respiratory chain and
fermentation. Table 1shows several redox potential of the reactions which take place in MFC.
The MFC electrical potential depends on the potential differences between the cathode and
the anode.
2.3. Microorganisms
Either microorganisms or enzymes can be used in biofuel cells, however applying
microorganism in biofuel cells allows multiple enzymes and, therefore, multiple substrates (or
mixed substrates) to be used. While purified enzymes can be used in specific and defined
reaction(s), this type of biofuel cells has been developed in biosensor technology in parallel
[Bullen et al., 2006]. MFC can be inoculated by pure or mixed culture of bacteria. Mixed
cultures are more beneficial in comparison with pure cultures due to their nutrient adaptability
and stress resistance [Mathuriya, 2013]. Application of rich and diverse source of bacteria,
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Factors Affecting the Performance of Microbial Fuel Cells
such as wastewater, activated sludge, soil or sediments in mediator-less MFCs is more
advantageous in wastewater treatment due to the presence of different kinds of bacteria
including electronics and giving a high power density[Logan, 2009; Mathuriya, 2013]. Table
1 presents Redox potential of various reactions in MFC electrodes.
Table 1 Redox potential of various reactions in MFC electrodes
2.4. Substrate
Great varieties of substrates which have been applied in MFCs vary from simple compounds
to complex mixtures of organic matters. In some cases, pure substrates such as glucose,
[Cheng et al., 2006] acetate,[Cheng and Logan, 2007] butyrate,[Liu et al., 2005]
lactate,[Futamata et al., 2013] proteins, cellulose, cysteine, glycine [Chen et al., 2014] and
glycerol were used. Acetate is anon fermentable substrate and a suitable electron donor
fordissimilatory iron-reducing bacterium which generate power up to 66% higher than
butyrate [Liu et al., 2005]. Among different substrates, wastewater is a sustainable rich
medium which can be treated by MFCs. There are several reports on electricity generation
directly from complex organic wastewater such as municipal,[ Liu et al., 2011] swine
wastewater, [Min et al., 2005] dairy wastewater, [Mardanpour et al., 2012; Venkata Mohan et
al., 2010] slaughter house wastewater,[Katuri et al., 2012] rice mill wastewater,[Behera et al.,
2010] tannery wastewater, [Mathuriya, 2013] cassava mill wastewater,[Kaewkannetra et al.,
2011] molasses wastewater,[Zhang et al., 2009] refinery wastewater,[Zhang et al., 2014]
brewery wastewater,[Mshoperi et al., 2011] winery wastewater,[Sciarria et al., 2015]
chemical wastewater,[Mohan et al., 2008; Raghavulu et al., 2009; Velvizhi et al., 2014]
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