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preferred during treatment of saline effluent and industrial wastewater in
MFC. Moreover, macrophytes or hydrophytes play an important role in phytoremediation in case of constructed wetland MFC due to plant metabolism to absorb
heavy metals and other nutrients [8]. Even in paddy field, methane emission can be
controlled by competition with electrogenic microbes, and hence methane emission
is reduced in paddy field MFC. On the other hand, locally available mixed culture
algae can support the high rate of biomass production and oxygen release for
cathodic reduction and mostly used for carbon sequestration in microbial carbon
capture cells. Thus, depending upon the characteristics of plants and local availability, plant species have been selected for MFC applications.
4.2 Operating Conditions
The operating conditions such as pH, salinity, and substrate flow and characteristics
and inoculum conditions control the rate of microbial metabolism during substrate
oxidation in MFC. In paddy fields, rice plants are sensitive for low salinity-deficient
conditions below the salinity level of 0.6 S/m [9]. In such conditions, electrolyte
salinity can be improved by addition of phosphate buffer solution in wastewater or
selection of seawater plant species for plant MFC. Similarly, increase of salt concentration in electrolyte also has negative impact on the growth of plant species in
MFC. Additionally, pH is one of the major indicators determining the proton gradient and flow between anodic and cathodic chamber. Most of plant metabolism are
best suited at neutral pH conditions and enhance the release of rhizodeposition from
plant roots [8]. In plant MFC, rate of rhizodeposition discharge depends on temperature conditions as well as humidity level which directly affect the current production in plant MFC.
4.3 Design Aspects
Electrode material selection mostly depends on the microbial attachment and biofilm formation, cost, and high conductive surface area. In case of sediment or plant
MFC, placing of electrodes in soil and maintaining the water interface control the
proton transfer diffusion. Deng et al. [5] studied the effect of electrode positions on
various soil and water depths. Results showed that MFC with 5-cm-deep soil and
3-cm overlaying water exhibited the highest power density of 0.72 mW/m
2
with
decrease in ohmic resistance. Also electron spacing is dependent on root zone depth
of plant as there is possibility of covering of anode with branches of roots and
unavailable for microbial biofilm growth. Lower electrode spacing supports the submergence of anode in a support matrix near the rhizosphere to obtain organic substrates in the influent as well as reduce the proton diffusion losses. Like typical
MFC, electrode material, architectural design, and catalyst selection affect the
energy recovery in plant MFC [10, 11].
Plant Microbial Fuel Cell as a Biomass Conversion Technology for Sustainable…
preferred during treatment of saline effluent and industrial wastewater in
MFC. Moreover, macrophytes or hydrophytes play an important role in phytoremediation in case of constructed wetland MFC due to plant metabolism to absorb
heavy metals and other nutrients [8]. Even in paddy field, methane emission can be
controlled by competition with electrogenic microbes, and hence methane emission
is reduced in paddy field MFC. On the other hand, locally available mixed culture
algae can support the high rate of biomass production and oxygen release for
cathodic reduction and mostly used for carbon sequestration in microbial carbon
capture cells. Thus, depending upon the characteristics of plants and local availability, plant species have been selected for MFC applications.
4.2 Operating Conditions
The operating conditions such as pH, salinity, and substrate flow and characteristics
and inoculum conditions control the rate of microbial metabolism during substrate
oxidation in MFC. In paddy fields, rice plants are sensitive for low salinity-deficient
conditions below the salinity level of 0.6 S/m [9]. In such conditions, electrolyte
salinity can be improved by addition of phosphate buffer solution in wastewater or
selection of seawater plant species for plant MFC. Similarly, increase of salt concentration in electrolyte also has negative impact on the growth of plant species in
MFC. Additionally, pH is one of the major indicators determining the proton gradient and flow between anodic and cathodic chamber. Most of plant metabolism are
best suited at neutral pH conditions and enhance the release of rhizodeposition from
plant roots [8]. In plant MFC, rate of rhizodeposition discharge depends on temperature conditions as well as humidity level which directly affect the current production in plant MFC.
4.3 Design Aspects
Electrode material selection mostly depends on the microbial attachment and biofilm formation, cost, and high conductive surface area. In case of sediment or plant
MFC, placing of electrodes in soil and maintaining the water interface control the
proton transfer diffusion. Deng et al. [5] studied the effect of electrode positions on
various soil and water depths. Results showed that MFC with 5-cm-deep soil and
3-cm overlaying water exhibited the highest power density of 0.72 mW/m
2
with
decrease in ohmic resistance. Also electron spacing is dependent on root zone depth
of plant as there is possibility of covering of anode with branches of roots and
unavailable for microbial biofilm growth. Lower electrode spacing supports the submergence of anode in a support matrix near the rhizosphere to obtain organic substrates in the influent as well as reduce the proton diffusion losses. Like typical
MFC, electrode material, architectural design, and catalyst selection affect the
energy recovery in plant MFC [10, 11].
Plant Microbial Fuel Cell as a Biomass Conversion Technology for Sustainable…