using these novel technologies, online monitoring of various parameters related to
water quality such as biological oxygen demand, toxicity, and total organic carbon is
achievable.
Keywords Fuel cells · Microbial fuel cells · Wastewater treatment · Biosensors ·
Electricity generation
1 Introduction
In these days, energy as a guaranty for the economic status of many countries all over
the world is a key and vital issue to be expressed. Moreover, fossil fuels (FCs) as the
main source of energy produce harmful and problematic pollution for our living
environment (Rahimnejad and Najafpour 2018). As a result, finding appropriate,
cost-effective, and cheap alternatives to use instead of FCs is an emergency nowadays (Logan 2004). To reduce CO 2 emission and global warming, great attentions
have been paid to renewable energy sources recently. Furthermore, electricity is one
of the most important preferable and flexible form of energy produced by FCs (Bard
and Faulkner 2001; Daud et al. 2011). The concept of how to use FCs to convert
chemical energy into electricity was discovered by the German scientist Christian
Friedrich Schönbein in the early nineteenth century (Grote 2010; Guo et al. 1996).
Like batteries, FCs do not have the ability to save energy; they only can alter one
type of energy into another type without using the materials inside the cell. Considering the fact, anode and cathode electrodes and electrolyte or membrane would be
introduced as the three main parts of aforementioned cells. Based on the electrolytes
used by these cells, they can be classified into many groups such as zinc-air FCs,
solid oxide FCs, alkaline FCs, molten carbonate FCs, biological FCs (BFCs), and
formic acid FCs (Rahimnejad and Najafpour 2018). As a matter of fact, high
efficiency, high-power output, easy transportation, being compatible with environmental rules, and high-energy density are some of the most well-known advantages
of FCs. In addition, there are some disadvantages for them such as high cost of
catalysts, corrosive electrolytes, and the harsh conditions of operation (high temperature and pressure) (Palmer et al. 1995; Selman 1993). BFCs as one type of FCs
which basically consist of two compartments (anode and cathode chambers), substrates can be oxidized by microorganisms or enzymes resulting in the releasing of
protons and electrons. Then, protons and electrons go through the proton exchange
membrane (PEM) and external circuit, respectively. Consequently, by the reaction of
oxygen, electrons, and hydrogen ions, water molecules will be generated in cathode
compartment. Microbial fuel cells (MFCs), sedimentary MFCs (SMFCs), and enzymatic MFCs are three main types of BFCs which separately can be operated for
specific targets. MFCs can be introduced as a novel and cost-effective technology to
convert organic matters including lignocellulosic biomass and low-strength wastewater into electricity and also would be able to beneficially combine with
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M. Rahimnejad et al.
water quality such as biological oxygen demand, toxicity, and total organic carbon is
achievable.
Keywords Fuel cells · Microbial fuel cells · Wastewater treatment · Biosensors ·
Electricity generation
1 Introduction
In these days, energy as a guaranty for the economic status of many countries all over
the world is a key and vital issue to be expressed. Moreover, fossil fuels (FCs) as the
main source of energy produce harmful and problematic pollution for our living
environment (Rahimnejad and Najafpour 2018). As a result, finding appropriate,
cost-effective, and cheap alternatives to use instead of FCs is an emergency nowadays (Logan 2004). To reduce CO 2 emission and global warming, great attentions
have been paid to renewable energy sources recently. Furthermore, electricity is one
of the most important preferable and flexible form of energy produced by FCs (Bard
and Faulkner 2001; Daud et al. 2011). The concept of how to use FCs to convert
chemical energy into electricity was discovered by the German scientist Christian
Friedrich Schönbein in the early nineteenth century (Grote 2010; Guo et al. 1996).
Like batteries, FCs do not have the ability to save energy; they only can alter one
type of energy into another type without using the materials inside the cell. Considering the fact, anode and cathode electrodes and electrolyte or membrane would be
introduced as the three main parts of aforementioned cells. Based on the electrolytes
used by these cells, they can be classified into many groups such as zinc-air FCs,
solid oxide FCs, alkaline FCs, molten carbonate FCs, biological FCs (BFCs), and
formic acid FCs (Rahimnejad and Najafpour 2018). As a matter of fact, high
efficiency, high-power output, easy transportation, being compatible with environmental rules, and high-energy density are some of the most well-known advantages
of FCs. In addition, there are some disadvantages for them such as high cost of
catalysts, corrosive electrolytes, and the harsh conditions of operation (high temperature and pressure) (Palmer et al. 1995; Selman 1993). BFCs as one type of FCs
which basically consist of two compartments (anode and cathode chambers), substrates can be oxidized by microorganisms or enzymes resulting in the releasing of
protons and electrons. Then, protons and electrons go through the proton exchange
membrane (PEM) and external circuit, respectively. Consequently, by the reaction of
oxygen, electrons, and hydrogen ions, water molecules will be generated in cathode
compartment. Microbial fuel cells (MFCs), sedimentary MFCs (SMFCs), and enzymatic MFCs are three main types of BFCs which separately can be operated for
specific targets. MFCs can be introduced as a novel and cost-effective technology to
convert organic matters including lignocellulosic biomass and low-strength wastewater into electricity and also would be able to beneficially combine with
216
M. Rahimnejad et al.