The document discusses microbial fuel cells (MFCs), which generate electricity through the catalytic reactions of microorganisms. It describes the basic components and principles of MFCs, including how bacteria at the anode convert organic substrates into protons and electrons. The protons pass through a membrane to the cathode, where the electrons from the external circuit also travel to recombine with the protons and oxygen, producing water. The document outlines various MFC designs, microbes, substrates, and applications. While MFCs can simultaneously treat wastewater and generate electricity, the technology still has low power densities and high costs compared to other energy sources.

1. Presented by
SHABEEBA.V
4PA11BT023

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

8. CONSTRUCTION OF MFC:

9. Components of MFC
 Anode
 Cathode
 Exchange membrane
 Substrate
 Electrical circuit
 Microbes

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

15. Substrates used in MFC
Substrate type Concentrations Current density
(m A/cm2)
Acetate 1g/L 0.8
Lactate 18mM 0.005
Glucose 6.7Mm 0.7
Sucrose 2674mg/L 0.19
Glucaronic acid 6.7mM 0.18
Phenol 400mg/L 0.1
Sodium fumerate 25mM 2.05
Starch 10g/L 1.3
Cellulosic particles 4g/L 0.02
Xylose 6.7mM 0.74
Domestic wastewater 600mg/L 0.06
Brewery wastewater 2240mg/L 0.2

16. Microbes used in MFC
 Axenic bacterial culture
 Metal reducing bacteria
 Shewanella putrefaciens
 Geobacter sulfurreducens
 Rhodoferax ferrireducens
 Clostridium beijerinckii
 Mixed bacterial fuel culture
 Desulfuromonas,
 Alcaligenes faecalis,
 Enterococcus faecium,
 Pseudomonas aeruginosa,
 Proteobacteria,

17. Continuation…..
 Clostridium butricum
 Bacteroides and
 Aeromonas species
 nitrogen fixing bacteria (e.g. Azoarcus and Azospirillum)

18. Working of MFC

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

22. Types of MFCs
 Mediator MFC
 Mediator free MFC
 Microbial electrolysis fuel cell

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
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