Recent developments in microbial fuel cell

RECENT DEVELOPMENTS
IN
MICROBIAL FUEL CELL
PRESENTED BY
SREENATH VN
1

CONTENTS
INTRODUCTION
HISTORY
WHAT ARE MICROBIAL FUEL CELL?
PRINCIPLE
CONSTRUCTION OF MFC
COMPONENTS
WORKING
MFC DESIGN
TYPES
APPLICATION
ADVANCES IN MFC
AVANTAGES
LIMITATIONS
2

INTRODUCTION
 Use of the fossil fuels can trigger global energy crisis and increased
global warming.
 Renewable bioenergy is considered as one of the ways to alleviate
the current global warming crisis.
 Microbial Fuel Cells have the potential to simultaneously treat
wastewater for reuse and to generate electricity.
 Microbial fuel cell technology represents a new form of renewable
energy.
3

HISTORY
M.C Potter was the first to perform work on the subject in 1911 in
E.coli.
In 1931, Barnet Cohen drew created a number of microbial half
fuel cells with 35 volts and 2milliamps.
In 1911 B.H. Kim developed mediator less MFC.
Microbial fuel cells have come a long way since the early 20th
century.
4

WHAT ARE MICROBIAL FUEL CELLS?
Chemical energy to electrical energy
Catalytic reaction of microorganisms
Bio-electrochemical system
Mimics bacterial interaction
5

PRINCIPLE
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.
6

COMPONENTS
Anode
Cathode
Exchange membrane
Substrate
Electrical circuit
Microbes
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Anode;
Conductive, bio compatible & chemically 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
9

Cathode;
Electrons and protons recombine at the cathode
O2 reduced to water
Pt catalyst is used
10

Exchange Member;
NAFION or ULTREX
Protons flows through the Exchange Membrane.
Proton and electrons recombine on the other side.
Can b a proton or cation exchange membrane
Electrical Circuit;
After leaving anode, electrons travel through the circuit
These electrons power the load
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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
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Microbes used in MFC;
Mediator based bacteria Mediator less bacteria
Actinobacillus succinogenes Aeromonas hydrophila
Erwinia dissolven Geobacter metallireducens
Proteus mirabilis G. sulfurreducens
Pseudomonas aeruginosa Rhodoferax ferrireducens
Shewanella oneidensis Shewanella putrefacien
Streptococcus lactis
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WORKING
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+ +8eacetate
Cathodic reaction:
O2 + 4e- + 4 H+ → 2 H2O
14

MFC DESIGN
Different configurations are possible
Widely used is a two chamber MFC built in traditional ‘H’ shape
various types of material can be used like plastic and stainless still
with coating
Two chamber connected by a tube containing a seperator usually
CEM or plain salt bridge
Material of the electrode can be of carbon or graphite
Carbon brush or carbon clothes can be used as an electrode.
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TYPES
Mediator MFC;
These will be made possible by different types of mediators.
These different types of mediators include methyl blude, methyl
viologen, thionine, and humic acid.
Mediator less MFC;
There is an active bacterium that is electrochemically
transferred to from the electrons into the electrode.
These specific electrons are actually carried directly to the
electrode from the enzyme in the bacterial respiratory.
16

Microbial Electrolysis Fuel Cell;
One variation of the mediator-less MFC is the microbial electrolysis cell
(MEC)
MFCs produce electric current by the bacterial decomposition of organic
compounds in water
MECs partially reverse the process to generate hydrogen or methane by
applying a voltage to bacteria.
17

Phototrophic Biofilm;
use a phototrophic biofilm anode containing photosynthetic microorganism
such as chlorophytacandyanophyta.
They carry out photosynthesis and thus produce organic metabolites and
donate electrons.
18

Ceramic Membrane;
PEM membranes can be replaced with ceramic materials.
The macroporous structure of ceramic membranes allows good
transport of ionic species.
The materials that have been successfully employed in ceramic MFCs
are earthenware, alumina, mullite, pyrophyllite and terracotta.
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APPLICATIONS
Electricity Generation;
MFCs are capable of converting chemical compounds in biomass to
electrical energy with the aid of microorganisms.
Chemical energy from the oxidization of fuel molecules is converted
directly into electricity.
Higher conversion efficiency can be achieved (>70%) just like
conventional chemical fuelcells.
20

Biohydrogen;
 Hydrogen generation from the protons and the electrons produced by
the metabolism of microbes in an MFC
 Applied an external potential to increase the cathode potential in a
MFC circuit and thus overcame the thermos dynamic barrier.
 In this mode, protons and electrons produced by the anodic reaction
are combined at the cathode to form hydrogen.
21

Biosensor;
 They can also be used as a convenient biosensor for waste
water streams.
Wastewater is evaluated based on the amount of BOD.
As an added bonus, the MFC biosensors power themselves
from the waste water.
22

Waste water Treatment;
The most immediately foreseeable application of an MFC is
in waste water treatment.
metabolize the carbon rich sewage of a waste water stream
to produce electrons that can stream into a carbon cloth
anode.
The electricity generated from the MFC also offsets the
energy cost of operating the plant.
 The company Emefcy in Israel claims to be able to cut sludge
down by 80% in their waste water treatment processes.
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ADVANCES IN MFC
In recent years, rapid advances have been made in MFC research
The microbial metabolism in MFCs was explained by Rabaey and
Verstraete (2005)
In (2006) Described both the properties of electrochemically active
bacteria used in mediator less MFC and the rate limiting steps.
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ADVANTAGES
Generation of energy out of biowaste / organic matter
Direct conversion of substrate energy to electricity
Omission of gas treatment
Aeration
Bioremediation of toxic compounds
25

LIMITATIONS
Low power density
High initial cost
Activation losses
Ohmic losses
Bacterial metabolic losses
26

Recent developments in microbial fuel cell

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