Transcript Introduction To Microbial Fuel Cell Technology

Bioreactor Design
Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
• Oil will not appreciably run out for at least 100 years or more, demand for oil
is expected to exceed.
• The costs of energy and how much energy we use will come to dominate our
economy and our lifestyle.
• The total annual energy consumption = 13.5 *1012 W (2006).
• Global demand of 41 * 1012 W in 2050.
• The release of stored carbon in fossil fuels is increasing the concentration of
carbon dioxide in the atmosphere. (from 316 ppmv in 1959 to 377 ppmv in
2004).
• By 2100, C02concentrations will reach from 540 to 970 ppmv.
• If we obtain energy from these sources using conventional technologies, we
will release additional CO2, exacerbate environmental damage, and global
climate change.
Renewable Energy Resources
Our greatest environmental challenge is to simultaneously solve energy
production and CO2 releases.
• Nuclear fission
• Solar energy
• Geothermal
• Wind
• Hydroelectricity
• Biofuel
Thus, our best solution for both energy and climate appears to be heavy
investment in
, in terms of both research and
development.
Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
Energy Consumption In Iran
Total ultimate energy consumption in Iran was 1033.32 MBOE in 2006.
and increased at an average annual rate of 6% in 1996-2006.
• [1 barrel of oil equivalent (boe)].
• Iran’s ultimate energy consumption pattern over the last decades is inefficient
and contributes towards the excessive consumption of fossil fuels which
produces several quantities of pollutants and green house gases.
• Low price of energy and high subsidies.
• represent an effective incentive for inefficient energy consumption pattern
and accelerate energy consumption and environmental pollutions.
Analysis of Ultimate Energy Consumption by Sector in Islamic Republic of Iran /B. FARAHMANDPOUR∗, I. NASSERI, H. HOURI JAFARI Energy Management
Department/3rd IASME/WSEAS Int. Conf. on Energy & Environment, University of Cambridge, UK, February 23-25, 2008
Comparison Of Energy Consumption
Total Energy consumption in
iran(2007)
Total energy consumption in
USA(2003)
http://www.eia.doe.gov/cabs/Iran/Background.html /Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
• Microbial fuel cells (MFCs) have emerged in recent years as a promising yet
challenging technology.
• MFCs are the major type of bioelectrochemical systems (BESs) which
convert biomass spontaneously into electricity through the metabolic activity
of the microorganisms.
• MFC is considered to be a promising sustainable technology to meet
increasing energy needs, especially using wastewaters as substrates, which
can generate electricity and accomplish wastewater treatment simultaneously
• It may offset the operational costs of wastewater treatment.
A review of the substrates used in microbial fuel cells (MFCs) for sustainable energy production Deepak Pant *, Gilbert Van Bogaert, Ludo Diels, Karolien Vanbroekhoven
Microbial Fuel Cells (MFCs) Have Gained A Lot Of
Attention In Recent Years
The number of articles on MFCs. The data is based on the number of articles mentioning MFC in the
citation database Scopus in September’ 2009
A review of the substrates used in microbial fuel cells (MFCs) for sustainable energy production Deepak Pant *, Gilbert Van Bogaert, Ludo Diels, Karolien Vanbroekhoven
:
Chemistry of MFC: Anode
Chemistry of MFC: Cathode
Substrate : Acetate
TEA: Oxygen
Substrate : Glucose
TEA: Ferricyanide
Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New
Jersey (2007).
MFC Components:
• Anode: Anodic materials must be conductive, biocompatible, and chemically
stable in the reactor solution.
• Anode Material: Carbon Paper, Cloth, Carbon Rod, Foams, Reticulated
Vitrified Carbon RVC ,Graphite Fiber, Graphite Rods, Felt, Plates, Graphite
Granules, And Sheets, Woven Graphite.
The highest specific surface areas and porosities
MFC Components:
Cathode
• Air cathods
• Aqueous catholytes :
Ferricyanide, Permanganate, iron
Abiotic
Biotic (biocathods)
MFC Components:
• Cathode: The same materials that have been described for use as the
anode have also been used as cathodes.
• Catalysts
• Electrode
• Binder
• Catholye
• catalyst is usually (i.e., Pt for oxygen reduction) but not always needed
(i.e., ferricyanide).
• The chemical reaction that occurs at the cathode is difficult to engineer as
the electrons, protons and oxygen must all meet at a catalyst in a tri-phase
reaction (solid catalyst, air, and water).
MFC Components:
• Membrane : primarily used as a method for keeping the anode and cathode
liquids separate.
• Cation or Anion Exchange Membranes, or any permeable material, can
function as a solution barrier in an MFC if charge can be transferred.
• Membrane material: Cation exchange membranes (CEM) CMI-7000, PEM
Nafion 117,AEM ,Bipolar Memrane , Ultrafiltration (UF) Membranes.
MFC Reactor Configurations:
Double Chamber MFC
Two-chamber air-cathode cube type MFC
• it useful to examine the effect of different
membrane types under similar conditions.
• High internal resistance
• Low power density
Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
Single Chamber Air-cathode Cube System
• A useful and simple design for
examination factors.
• Substrate:Glucose
• P=494± 21 (no CEM).
• P=262±10 ( CEM).
Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007). Energy Sustainability of the Water
Infrastructure Bruce E. Logan Penn State University (2008)
Tubular MFC With Inner Cathode Compartment
• SCAC MFC :a cathode tube concentric with eight
graphite anodes in an acrylic tube casing.
• This reactor was used to demonstrate electricity
production with simultaneous wastewater treatment.
[Liu et a/. (2004).
Microbial fuel cells: novel biotechnology for energy generation Korneel Rabaey and Willy Verstraete. TRENDS in Biotechnology Vol.23 No.6 June (2005).
Tubular Upflow Reactor Designs
• Anode & Cathod:(RVC)
• The flow was directed towards the CEM
• Internal resistance =84 Ω (limited
power production)
•Anode :conductive graphite granules
• Cathode:thick woven graphite mat
• Catholyte:ferricyanide
Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New Jersey
(2007).
• Direct contact through outer-membrane proteins.
• Diffusion of soluble electron shuttles.
• Dlectron transport through solid components of the extracellular
biofilm matrix.
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee,
Prathap Parameswaran, Rosa Krajmalnik-Brown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
Mechanisms Of Electron Transfer
Mechanisms Of Electron Transfer
• Direct contact of anode-respiring bacteria cannot achieve high current
densities due to the limited number of cells.
• Slow diffusive flux of electron shuttles at commonly observed
concentrations limits current generation and results in high potential
losses.
• Only electron transport through a solid conductive matrix can explain
observations of high current densities and low anode potential losses.
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran, Rosa
Krajmalnik-Brown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
Solid Conductive Matrix Mechanism
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran, Rosa
Krajmalnik-Brown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
BOTTLENECKS OF MICROBIAL FUEL CELLS
• Anode compartment: potential losses decrease MFC voltage.
• Transport of charge and ions in the electrolyte: the influence of turbulence.
• Membrane resistance, selectivity and O2 permeability.
• The structure of the anode
• The role of the cathode performance
Microbial fuel cells: performances and perspectives /Korneel Rabaey, Geert Lissens and Willy Verstraete.(2005).
Polarization Curve In Fuel Cells
• Activation overpotentials: major limiting factor in MFC
Voltage losses due to bacterial metabolism
• Ohmic losses :intarnal resistance
• Concentration polarization:
Microbial fuel cells: performances and perspectives /Korneel Rabaey, Geert Lissens and Willy Verstraete.(2005).
Activation Overpotential
Activation losses are due to energy lost (as heat) :
• Voltage losses due to bacterial metabolism : bacteria need sufficient energy only
to pump one proton across a membrane.
• Reducing a compound at the bacterial surface requires certain energy to
activate the oxidation reaction.
• Energy lost through the transfer of an electron from the cell terminal protein to
the anode surface. ( the nanowire, mediator, or terminal cytochrome at the cell
surface).
• Oxidizing a compound at the anode surface.
Microbial fuel cells: performances and perspectives /Korneel Rabaey, Geert Lissens and Willy Verstraete(2005)/ Microbial fuel cell Bruce E. Logan The Pennsylvania State
UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
potential losses (Edonor-Eanode)
Edonor-EOM
EOM-Einterface
Einterface-Eanode
Edonor-Eanode
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran, Rosa
Krajmalnik-Brown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
j: current density obtained by ARB
jmax: the maximum current density of the ARB biofilm,
S : the substrate concentration in the liquid
Ks, app: the apparent half-saturation substrate
concentration in a biofilm.
R: ideal gas constant (8.3145 J mol^-1 K^-1)
F:Faraday constant (96 485 C mol^-1 e-)
T: temperature (K)
EKA: the potential at which j = 1/2jmax (V)
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran, Rosa Krajmalnik-Brown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
Solid conductive matrix mechanism
(EOM-Einterface)
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran, Rosa KrajmalnikBrown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
kinetic perspective on extracellular electron transfer by anode-respirA ing bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran, Rosa Krajmalnik-Brown & Bruce E.
Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
Schematic of three EET mechanisms used
Several Solutions To Reduce Activation Loss
• Increasing the operation temperature
• Decreasing the activation losses at the electrode surface
Addition of a catalyst to the electrode
Increasing the roughness and specific surface of the electrode
• Decreasing the activation losses at the bacteria
A redox mediator can be added to the anode compartment
Microbial fuel cells: performances and perspectives /Korneel Rabaey, Geert Lissens and Willy Verstraete(2005)/ Microbial fuel cell Bruce E. Logan The Pennsylvania State
UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
Ohmic Overpotential
resistance of only 15 Ω
potential loss of 150 mV
Microbial fuel cells: performances and perspectives /Korneel Rabaey, Geert Lissens and Willy Verstraete(2005)/ Microbial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
Concentration Polarization (Mass Transfer Losses)
• This is a problem only occurring at higher current densities
• When the flux of reactants to the electrode or the flux of products from the
electrode are insufficient and therefore limit the rate of reaction.
• Thick non-conductive biofilm
• Substrate flux
• Proton flux from the anode
Microbial fuel cells: performances and perspectives /Korneel Rabaey, Geert Lissens and Willy Verstraete(2005)/ Microbial fuel cell Bruce E. Logan The Pennsylvania State
UniversityPub John Wiley . Inc., Hoboken, New Jersey (2007).
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But wait…
There’s More!
Supplementary Information
Direct Contact Mechanism
• We calculate the maximum current density achievable by this monolayer
biofilm using a simple biofilm model.
jmax is a function of the active biofilm thickness according to the following
equation
Soluble electron shuttle mechanism
• The use of electron shuttles allows ARB to be located away from the anode
surface and to accumulate more than a monolayer of bacteria.
• Although shuttles allow more ARB to be active per anode surface area, the
distance between ARB and the anode becomes a limiting factor due to
diffusion limitations of the electron shuttles (Picioreanu et al., 2007).
Soluble electron shuttle mechanism
• transport of soluble electron shuttles is mainly carried out by diffusion
through Fick’s law, shown here modified to reflect current density
calculations:
Dshuttle : the diffusion coefficient of the electron shuttle (m2 /s1)
Δz : the transport distance (m),
Δcshuttle : the concentration gradient of either oxidized or reduced shuttle
(mol/m3),
nF :converts from moles to coulombs.
Soluble electron shuttle mechanism
• The total current density obtained by ARB using electron shuttles can be
limited by the diffusion of electron shuttles according to Eqn. (5).
• Diffusion coefficients of organic molecules are relatively small, indicating
that diffusion is an inherently slow process.
• if we can assume electron shuttles is similar to other organic molecules, such
as glucose, then Dshuttle ≈ Dglucose=6.7 *10^-10 (m2 /s)
Soluble electron shuttle mechanism
• ΔCshuttle is limited by the total concentration of electron
• shuttles present in the ARB biofilm.
Dshuttle=6.7 *10^-10 (m2 /s).
• ΔCshuttle=1µM=1*10^-3( mol/m3), and n = 2 for the electron shuttle
reaction (Kubota & Gorton, 1999; von Canstein et al., 2008),
• the flux of an electron shuttle across 1 mm of biofilm
• (Δz=1mm) is only 0.13 (A/m2).
• This calculated value is 100 times smaller than observed current densities.
Soluble electron shuttle mechanism
• The potential loss for an electron-shuttle reaction
•
can be calculated by the Nernst equation:
• The value for E0 is also an important parameter to characterize the potential
loss of electron shuttles, as it at which the current density approaches zero (j0)
by Butler–Volmer kinetics
Soluble electron shuttle mechanism
• Loss of electron shuttles in the effluent of the MXC poses Another challenge
to its use by ARB.
• A few studies showed a decrease in current density when the medium was
replaced in batch experiments using ARB that produce electron shuttles
(Bond & Lovley, 2005; Marsili et al.,2008a).
• This effect could be stronger in a continuous system, where the steady loss of
electron shuttles in the effluent liquid decreases their concentration in the
biofilm significantly.
• Marsili et al. (2008a) have proposed that electron shuttles can be at higher
concentrations inside the biofilm by binding to the electrode surface and
biomass.
• Binding cannot increase the flux of electrons throughdiffusion, because the
attached shuttles cannot diffuse.
Solid conductive matrix mechanism
• It is also unknown whether nanowires are themselves conductive or whether
they serve as a surface for conductive proteins/polymers to attach.
• Recent studies have shown that ARB known to produce a solid conductive
matrix can produce high current densities.
j0 : the exchange current density (A/m2)
α : the electron-transfer coefficient or the symmetry coefficient for the anodic
or the cathodic reaction
Eanode : the anode potential (V)
E0interface :the standard potential (V) of the reaction occurring at the anode
interface.
• this reaction can occur between a protein and the anode or by a compound
(such as an electron shuttle) and the anode.
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran, Rosa
Krajmalnik-Brown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
Summary of kinetic analysis on the three EET
mechanisms known to be used by ARB
•
A kinetic perspective on extracellular electron transfer by anode-respiring bacteria /C´ esar I. Torres, Andrew Kato Marcus, Hyung-Sool Lee, Prathap Parameswaran,
Rosa Krajmalnik-Brown & Bruce E. Rittmann./FEMS Microbiol Rev 34 (2010) 3–17
units
• ppmv= ppm by volume (i.e., volume of gaseous pollutant per 106 volumes of
ambient air).
• The SI unit of conductivity is siemens per meter (S/m).
• 1siemens = reciprocal of one ohm