and represent yet another promising and challenging technology for the sustainable
production of energy. MFCs are bioelectrochemical systems (BESs) which convert
biodegradable organic waste including wastewaters and lignocellulosic biomass into
electricity through microbial metabolic activity. They are considered mainly for
using wastewater as a substrate to accomplish its treatment (mineralization of
organic carbon into CO 2 ) and to meet increasing energy demand by generating
electricity simultaneously. This surge offsets the costs of wastewater treatment
plants’ operations (Lu et al. 2009). Different substrates were explored as a feed
which includes various kinds of artificial and real wastewaters and biomass from
algae and plants (Pant et al. 2010).
4.2.1 Design Principle and Operation of MFC
An MFC functions like an electrochemical cell in that it consists of anodic and
cathodic chambers separated by an ion-selective membrane. In the anodic chamber,
microorganisms anaerobically oxidize biomass or organic matter to produce electrons and protons. Electrons then flow through an external circuit to the cathode
(flow of current), while protons go through the membrane to the cathode. Electrons
and protons are then consumed by an electron acceptor (mainly oxygen) in the
cathode to produce water. A variety of electron acceptors includes metal ions like Fe
(III), Cr (VI), and Mn (V), inorganic electron acceptors like sulfates, and microorganisms such as denitrifying bacteria and microalgae (Wang et al. 2008; Gouveia
et al. 2014).
Different combinations of microorganisms used in MFC as the substrate, electron
donor, and acceptor are as follows: (i) bacteria as an electron donor in the anode
compartment (Xing et al. 2008); (ii) microalgae in both cathode and anode compartments (Gouveia et al. 2014); (iii) bacteria (electron producer) + microalgae
biomass (as substrate) in the anode compartment (Strik et al. 2008); and
(iv) bacteria (electron producer) in anode and microalgae in the cathode chamber
for oxygen production (electron acceptor) (Gouveia et al. 2014).
Based on the MFC design, there is the two-chambered (Fig. 13.6a) and singlechambered (Fig. 13.6b) system where the former is the traditional (two compartments) method. The two-chambered system has disadvantages, such as large volume, low power output, and costs for aeration (Lu et al. 2009). Simpler and more
efficient MFCs were developed by neglecting the cathode compartment. That is, the
single-chambered MFCs consist of a cathode electrode on the membrane directly
exposed to the air.
4.2.2 Current and Power Outputs from MFCs with Different Substrates
The generation of current in MFCs is directly related to the ability of the bacteria to
oxidize a given substrate and electrons transport to the anode electrode. The current
density and the efficiencies in removing pollutants also differ according to the
13 Phycoremediation: An Integrated and Eco-friendly Approach for. . .
321
production of energy. MFCs are bioelectrochemical systems (BESs) which convert
biodegradable organic waste including wastewaters and lignocellulosic biomass into
electricity through microbial metabolic activity. They are considered mainly for
using wastewater as a substrate to accomplish its treatment (mineralization of
organic carbon into CO 2 ) and to meet increasing energy demand by generating
electricity simultaneously. This surge offsets the costs of wastewater treatment
plants’ operations (Lu et al. 2009). Different substrates were explored as a feed
which includes various kinds of artificial and real wastewaters and biomass from
algae and plants (Pant et al. 2010).
4.2.1 Design Principle and Operation of MFC
An MFC functions like an electrochemical cell in that it consists of anodic and
cathodic chambers separated by an ion-selective membrane. In the anodic chamber,
microorganisms anaerobically oxidize biomass or organic matter to produce electrons and protons. Electrons then flow through an external circuit to the cathode
(flow of current), while protons go through the membrane to the cathode. Electrons
and protons are then consumed by an electron acceptor (mainly oxygen) in the
cathode to produce water. A variety of electron acceptors includes metal ions like Fe
(III), Cr (VI), and Mn (V), inorganic electron acceptors like sulfates, and microorganisms such as denitrifying bacteria and microalgae (Wang et al. 2008; Gouveia
et al. 2014).
Different combinations of microorganisms used in MFC as the substrate, electron
donor, and acceptor are as follows: (i) bacteria as an electron donor in the anode
compartment (Xing et al. 2008); (ii) microalgae in both cathode and anode compartments (Gouveia et al. 2014); (iii) bacteria (electron producer) + microalgae
biomass (as substrate) in the anode compartment (Strik et al. 2008); and
(iv) bacteria (electron producer) in anode and microalgae in the cathode chamber
for oxygen production (electron acceptor) (Gouveia et al. 2014).
Based on the MFC design, there is the two-chambered (Fig. 13.6a) and singlechambered (Fig. 13.6b) system where the former is the traditional (two compartments) method. The two-chambered system has disadvantages, such as large volume, low power output, and costs for aeration (Lu et al. 2009). Simpler and more
efficient MFCs were developed by neglecting the cathode compartment. That is, the
single-chambered MFCs consist of a cathode electrode on the membrane directly
exposed to the air.
4.2.2 Current and Power Outputs from MFCs with Different Substrates
The generation of current in MFCs is directly related to the ability of the bacteria to
oxidize a given substrate and electrons transport to the anode electrode. The current
density and the efficiencies in removing pollutants also differ according to the
13 Phycoremediation: An Integrated and Eco-friendly Approach for. . .
321