This document summarizes a study on a plant microbial fuel cell (PMFC). The PMFC generates electricity from the natural interaction between plant roots and soil bacteria. The study constructed a PMFC using a terracotta pot with a graphite anode and zinc cathode. Voltage increased over time as microbes broke down compounds from plant roots. The PMFC achieved steady voltages of 0.88V for a mud-based MFC and 1.01V. PMFCs provide renewable energy without biomass transport and utilize plant-microbe interactions.

1. Presented by
Deepti Bansod,Tulika Srivastava,K.Sudhakar
Energy Centre,
Maulana Azad National Insitute of
Technology,Bhopal,M.P
ICAER 2013,IIT
Bombay

2. 
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A microbial fuel cell is a device that converts chemical energy to
electrical energy by the catalytic reaction of microorganisms.
A microbial fuel cell (MFC) or biological fuel cell is a bioelectrochemical system that drives a current by using bacteria and
mimicking bacterial interactions found in nature.
Microbial Fuel Cell (MFC) technology generates either electricity
or hydrogen from bacterial growth in carbon-containing solutions,
including sources of low or negative economic value such as
wastewater.

3. The operating principles of a microbial fuel cell. Electrons can flow to the anode via
chemical mediators or directly.

4. 
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Electrons produced by the bacteria from these substrates are
transferred to the anode (negative terminal) and flow to the
cathode (positive terminal) linked by a conductive material
containing a resistor, or operated under a load .
By convention, a positive current flows from the positive to the
negative terminal, a direction opposite to that of electron flow.
Electrons can be transferred to the anode by electron mediators or
shuttles , by direct membrane associated electron transfer , or by
so-called nanowires produced by the bacteria, or perhaps by other
as yet undiscovered means.
In most MFCs the electrons that reach the cathode combine with
protons that diffuse from the anode through a separator and
oxygen provided from air; the resulting product is water.

5. 
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The potential difference between the anode and the cathode,
together with flow of electrons, results in the generation of
electrical power.
Unfortunately, this reaction is not kinetically catalyzed. In order to
obtain sufficient oxygen reduction reaction rate a precious metalcatalyst such as platinum to the cathode.

6. An MFC apparatus was employed that consisted of a
20 Litre cylindrical plastic container of dimension 30
cm height and 28 cm diameter.
 A rectangular solid graphite of (28 cm x 10cm x 15
cm) was used as anode and buried inside the mud.
 A rectangular zinc cathode plate of (14 cm x 4 cm) was
placed on the top surface of the bucket filled with
water.
 All the electrodes were clean and used as received;
they were conducted out with copper wire.


7. Fig. Schematic representation, Photograph of the MFC and electrodes

8. •Copper wire leads contacting the anode and cathode surfaces were
connected with various resistances ranging from 10 Ω to 500 Ω resistor.
•A digital multimeter (RISH multi 15S) was used to measure voltage
produced by the MFCs at intervals of one hour .
•Voltage (v) and current (mA) was measured across the external resistor
connected between the anode and cathode.
• Current density and power density were calculated by dividing I and P by
the anode surface area.
•Power (P) was calculated according to P = V * I (mW).
•Power density (p) was calculated according to p= P/A. The anode area
was used to calculate current density and power density. Power density (p)
was calculated according to p= P/A (mW/m2).
•Current density(i) was calculated as i = I/A(mA /m2) where A (cm2) is
the projected surface area of the anode.

9. 
The output voltage was monitored for the whole day. The power
output and voltage of MFC increased gradually because of the
biological activity of microorganism.

The voltage reached from the initial value of 0.56V to 0.88 V
during the 1st day. The steady state voltage of cell was maintained
at 0.88V over the complete cycle.
When the cell reached to the stable condition, polarization curve
was obtained by changing the external resistance. The maximum
current density of MFC was 50.69 mA/m2 for the steady phase.
The polarization curve as a function of current density and power
density measured at variable resistances (10Ω-500Ω). Current
generation in different resistors was observed once the MFC
attained the maximum voltage

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10. 
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Current and power density showed decreasing trend with
increasing in resistance and is consistent with the reported
literature, which indicated a typical fuel cell behaviour.
At higher resistance used (500Ω), relatively less power density of
27.08 mW/m2 was observed.
Relatively less drop and constant voltage was observed at various
resistances studied. Maximum power peak in this period was
equal to 1.92 mw.

11. TIME
Voltage(V)
10.00AM
0.56
10.30AM
0.57
11.00AM
0.58
11.30AM
0.59
12.00PM
0.59
12.30PM
0.60
1.00PM
0.65
1.30PM
0.68
2.00PM
0.69
2.30PM
0.78
3.00PM
0.85
3.30PM
0.88
4.00PM
0.88
4.30PM
0.88

12. 1
0.9
0.85 0.88 0.88 0.88
0.8
0.78
0.7
0.6
0.5
0.57
0.59
0.58
0.59
0.65
0.6
0.68 0.69
0.4
0.3
0.2
0.1
0
Voltage(V)

13. 
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The unswerving conversion of substrate energy to electricity
enables high conversion efficiency.
MFCs operate efficiently at optimum and even at
low, temperatures distinguish them from all present bio-energy
processes.
MFC have become popular as it has the capacity to produce
energy in the form of electricity or hydrogen from renewable
sources like industrial or household waste.
It uses organic squander stuff as fuels and easily available
microbes as catalysts.
Since microbial fuel cells can be setup at remote locations where
water resources exist, they are a convenient power source for
remote environmental sensors.

14. 
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MFC technology is still elementary and there are several areas for
development.
Traditional MFC show low columbic efficiencies due to
ineffective electron transfer linking the microbial cells, and the
anode.
This ineffectiveness consequence in partial oxidation of the fuel
and unsought digestion of some of the fuel carbon in to biomass.
However the problem with MFCs is that their power generation
(the rate of electron abstraction) is still very low.

16. •
•
•
•
The PMFC is a technology that uses electrochemically active
bacteria as a catalyst to oxidize organic and inorganic matter to
generate current.
The microbial fuel cell consists of an anode compartment where
the electrons are released by electrochemically active bacteria and
transferred to the electrode.
Plant-Microbial Fuel Cell generates electricity from the natural
interaction between plant roots and soil bacteria.
Microbes living in the plant soil create ions by digesting excess
glucose from the plants

17. 
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The plant microbial fuel cell operates on the principle that
microbes are able to an-aerobically break down & release
electrons from the small molecular mass carbohydrates that are
exuded from the roots of plants as a result of photosynthesis.
During photosynthesis, the carbon dioxide fixed in the leaves is
converted to small molecular weight carbohydrates and are sent to
the plant roots where they are lost as root exudates.
In microbial decomposition, protons, electrons and carbon
dioxide are released.
The carbon dioxide release to the atmosphere
The protons and electrons are used for the production of
electricity as in the microbial fuel cell.

18. 
i.
ii.
The plant-MFC is based on two proven processes
Rhizo-deposition of organic compounds by living plants
electricity generation from organic compounds in the microbial fuel cell.
The principal idea is that plant rhizodeposits will be utilized as substrates
by the bacteria to generate electricity in the microbial fuel cell.
The basic working of PMFC:
(i) photosynthesis
(ii) transport of organic matter to the anode compartment
(iii) anodic oxidation of organic matter by electrochemically active bacteria
(iv) cathode reduction of oxygen
 Anode and Cathode compartment , mostly separated by a membrane separate the oxidation and reduction process.


19. 
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Plant Microbial Fuel Cell Aglaonema hybrids, was obtained from
Energy Centre, M.A.N.I.T, Bhopal.
constructed plant microbial fuel cells - based on an anode
compartment consisting of Terracotta flower pot with height of 35
cm and diameter of 18 cm.
Anode compartment - a graphite anode felt on the bottom
(length=15, breadth=5.15cm width=0.5cm)
zinc cathode (4x4 cm and 3mm thick)t is suspended in the water
column.
Naturally occurring micro-organisms were already present on the
roots of the plants at the time of placement into the plant-MFC.
The plant-MFC therefore contains a whole range of microorganisms, which was confirmed by microscopic analyses of
samples.

20. Fig. Schematic representation, Photograph of the PMFC and electrodes

21. Copper wire leads contacting the anode and cathode surfaces were
connected with various resistances ranging from 10 Ω to 500 Ω resistor.
A digital multimeter (RISH multi 15S) was used to measure voltage
produced by the MFCs at intervals of one hour .
Voltage (v) and current (mA) was measured across the external resistor
connected between the anode and cathode.
 Current density and power density were calculated by dividing I and P
by the anode surface area.
Power (P) was calculated according to P = V * I (mW).
Power density (p) was calculated according to p= P/A. The anode area
was used to calculate current density and power density. Power density (p)
was calculated according to p= P/A (mW/m2).
Current density(i) was calculated as i = I/A(mA /m2) where A (cm2) is
the projected surface area of the anode

22. TIME
VOLTAGE
1.00PM
0.68
1.10PM
0.69
1.20PM
0.70
1.30PM
0.78
1.40PM
0.89
1.50PM
0.91
2.00PM
0.95
2.10PM
0.96
2.20PM
0.97
2.30PM
0.98
2.40PM
0.99
2.50PM
0.99
3.00PM
1.00
3.10PM
1.01
3.20PM
1.01

23. Voltage(V)
1.2
1
1.01
0.8
0.68
0.6
0.4
0.2
0
Time

24.  The power output and voltage of PMFC increased gradually



because of the biological activity of microorganisms.
The voltage reached from the initial value of 0.68V to 1.01 V
during the 1st day. The steady state voltage of cell was maintained
at 1.01V over the complete cycle.
Though the steady state potential of 1.01V is very much
lower, but it was maintained for longer time period.
Even though theoretical power output is estimated at 3.2 W/m2
geometric planting area , power output obtained from this study
ranged only from 263 mW/m2 to 118 mW/m2 with plants as sole
organic matter source.

25. 1.2
1
0.8
Voltage
MFC VOLTAGE
0.6
P MFC VOLTAGE
0.4
0.2
0
9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM 4:00 PM 5:00 PM
Time

26. 
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Environmental advantages such as no transport of harvested
biomass, preservation of nutrients in the ecosystem, use of a
renewable energy source, no combustion or extra greenhouse gas
emissions during production.
Green Power Generation
Low temperature power generation
Renewable and Sustainable Energy Source
It can solve industrial energy concerns
Energy production is mostly in-situ
PMFC could be used to power small gadgets like LED
lights, laptops and cell phones.

27. 
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