2. CONTENTS
Introduction
What are fuel cells?
What are microbial fuel cells
principle
Construction of MFC
Components of MFC
Working of MFC
Thermodynamics of MFC
MFC Design
Types of MFC
Applications of MFC
Advantages of MFC
Limitations of MFC
Conclusion
References
3. INTRODUCTION
• Use of the fossil fuels can trigger global energy crisis and increased
global warming hence there is considerable interest in research
fraternity on green production
In an era of climate change, alternate energy sources are desired to
replace oil and carbon resources. Subsequently, climate change effects
in some areas and the increasing production of biofuels are also putting
pressure on available water resources.
Microbial Fuel Cells have the potential to simultaneously treat
wastewater for reuse and to generate electricity; thereby producing two
increasingly scarce resources
Microbial fuel cell technology represents a new form of renewable
energy by generating electricity from what would otherwise be
considered waste, such as industrial wastes or waste water etc
4. Continuation….
• M.C Potter was the first to perform work on the subject in 1911 in
E.coli,A professor of botany at the University of Durham
• In 1931, however, Barnet Cohen drew more attention to the area when
he created a number of microbial half fuel cells that, when connected
in series, were capable of producing over 35 volts, though only with a
current of 2 milliamps
• In 1911 B.H. Kim devoloped mediatorless MFC was a milestone in MFC,
Enhanced the commercial viablity,by eleiminating costly mediator
chemicals.
• Microbial fuel cells have come a long way since the early 20th century.
5. What are fuel cells?
Device that converts chemical energy from fuel into electricity through
chemical reaction with oxygen or another oxidizing agent.
6. What are Microbial fuel cells?
Chemical energy to electrical energy
Catalytic reaction of microorganisms
Bio-electrochemical system
Mimics bacterial interaction
primary flow diagram
7. Based on redox reactions
Harness the natural metabolism of microbes to produce electricity
Bacteria converts substrate into electrons
Electrons run through the circuit to generate power
Principle
10. Anode;
Conductive,bio compatible & chemicaly stable with substrate
Stainless steel mesh,graphite plates or rods
Bacteria live in the anode compartment and convert substrate to CO2,H2O
and energy
Bacteria are kept in an oxygen less environment
Anode compartment
11. Cathode;
Electrons and protons recombine at the cathode
O2 reduced to water
Pt catalyst is used
Cathode compartment
12. Exchange membrane;
NAFION or ULTREX
Protons flows through the EM
Proton and electrons recombine on the other side.
Can b a proton or cation exchange membrane
Exchange membrane
13. Electrical circuit
After leaving anode, electrons travel through the circuit
These electrons power the load
Electrical circuit
14. Substrates;
Substrates provide energy for the bacterial cell
Influences the economic viability and overall performance such as
power density and coloumbic efficiency of MFC
Concentration,composition and type
Organic substrates-carbohydrates, protein,volatile acids,cellulose and
waste water
Acetate is commonly used as substrate
19. Continuation…….
Anode and cathode separated by cathode specific membrane
Microbes at anode oxidize organic fuel generates electrons and protons
Protons move to the cathode compartment through the membrane
Electrons transferred to the cathode compartment through external
circuit to generate current
Electrons and protons are consumed in cathode chamber, combining
with O2 to form water
Anodic reaction:
CH3COO- + H2O → 2CO2 + 2H+ +8e-
acetate
Cathodic reaction:
O2 + 4e- + 4 H+ → 2 H2O
20. Thermodynamics of MFC
Using Gibbs free energy
∆G r = Gr
0 + RT ( lnπ)
Cell electromotive force
W = EemfQ = ∆Gr , Q = nF
Eemf = ∆ Gr∕ nF
Overall reaction in terms of the potential as
Eemf = E0
emf –RT∕nF ln(π)
positive for a favourabl reaction
directly produces a value of emf for the reaction
21. MFC Design
Different configurations are possible
Widely used is a two chamber MFC built in traditional ‘H’ shape
Two chamber connected by a tube containing a seperator usually
CEM or plain salt bridge
23. Continuation……
Soil based MFC
Phototrophic biofilm MFC
Nanoporous MFC
Sediment MFC
Membrane less MFC
24. Applications of MFC
Waste water treatment
Power generation
Secondary fuel production
Bio-Sensors
Desalination
Educational tool
25. Advantages of MFC
Generation of energy out of biowaste / organic matter
Direct conversion of substrate energy to electricity
Omission of gas treatment
Aeration
Bioremediation of toxic compounds
26. Limitations of MFC
Low power density
High initial cost
Activation losses
Ohmic losses
Bacterial metabolic losses
27. Conclusion
MFCs have been explored as a new source of electricity generation
during operational waste water treatment.
Phototropic MFCs and solar powered MFC also represent an
exceptional attempt in the progress of MFCs technology for electricity
production.
It can be used for production of secondary fuel as well as in
bioremediation of toxic compounds.
However, this technology is only in research stage and more research is
required before domestic MFCs can be made available for
commercialization
Provided the biological understanding increases, the electrochemical
technology advances and the overall electrode prices decrease, this
technology might qualify as a new core technology for conversion of
carbohydrates to electricity in years to come.
28. Reference
1.Microbial fuel cells.Retreived March 25,2015 from http://www.microbial fuel cell.org/www/
2.Electricity generation from microbial fuel cells.Retreivd March 25,2015.http://illumin.use.edu/printer/134/microbial-fuel-cells-generating-
power-from-waste/
3.Allen, B. (1993). Microbial fuel cells.electricity production from carbohydrates. 27-40.
4.Ashley, f. (2010, may-june). Microbial electrosynthesis,feeding microbes electricity to convert carbondioxide and water.
5.Badwal.SPS. (2014). Emerging electrochemical energy conversion and storage technologies. frontiers in chemistry, 79.
6.Bennetto. (1990). electricity generation by micro organisms.microbial ecology,1(4), 163-168.
7.Biffinger, j. C. (2007). diversifyin biological fuel cell design by use of nanoporous filters. enviornmental scince and technology, 1444-49.
8.Chen, T., Barton, & Binyamin. (2001, september). a miniature bio fuel cell. 123(35).
9.Cohen, B. (1931). The Bacterial culture as an Electrical half-cell. journal of bacteriology, 21, 18-19
10.DelDuca, M. a. (1963). Dovelopments in industrial microbiology.journal of industrial microbiology 4, 81-84.
11.Elizabeth, E. (2012). generating eectricity by nature way.Biotechnol 8,556-600
12.Gong, & Radachowasky. (n.d). benthic microbial fuel cell as direct power source for an acoustic modem and seawater oxygen/temperature
sensor system. environmental science and technolgy(11), 5047-53.
13.Helder, m. (2011). microbial solar cells:applying photosynthetic and electrochemically active organisms. trends in biotechnology, 41-49.
14.kim, p. (1999). direct electrode reaction of fe(III) reducing bacterium.shewanell putrifaciens.Nature 9, 127-131.
15.Lithgow, R. (1986). Interception of electron transport cain in bacteria with hydrophilic redox mediators. 178-179.
16.Matasunga, S. &. (1976). continuous hydrogen production by immobilized whole cells of Clostridium butrycum. 24:2, 338-343.
17.Min, B. L. (2005). Electricity genertion using membrane and salt bridge microbial fuel cell,water reasearch. 39(9), 1675-86.
18.Mohan, V., & raghavulu, v. (2008). influence of anodic biofilim growth on bio electricity production in single chamber meditaor less
microbial fuel cells. biosensors and bioelectronics, 24(1), 41-47.
19.Mohan, v., krishnan, M., & srikanth. (2008). harnessing of microbial fuel cell employin aerated cathode through anerobic treatment of
chemical wastewater using selectively enriched hydrogen producing mixed consortia. 87(12), 2667-2676.
20.Potter, M. (1911). electrical effects accompanying the decomposition of organic compounds. 84, 260-276.
21.Strik, D. (2008). Green electricity production with living plants and bacteria in a fuel cell. international journal of energy research, 32(9),
870-876.
Cellular respiration s a collection of metabolic reactions that cells use to convert nutrients into ATP which fuels cellular activity.overalll reaction is an exothermic redox reaction.
Meaning;mfc is a bec system that drives a current by mimicking bacterial interactions found in nature
Oxygen free enviornment:to promote the flow of electrons through anode
Pt catalyst:to reduce O2 sufficiently
Y acetate:due to its inertness towards alternative microbial conversions(fermentations and methenogenisis) that lead to high colombic efficiency and power output.
Mfc work by allowing bactera to do what dey do best,oxidize and reduce organic molecules
Bacterial respiration is basically one big redox reaction in which electrons being move around
Emf is potential difference bw cathode and anode.this is related to work W(J)