bioreactor design. oil will not appreciably run out for at least 100 years or more, demand for oil...

Lecturer: Sara Madani

Supervisor: Reza Gheshlaghi

Microbial Fuel Cell

Bioreactor Design

• 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, C 0 2 concentrations 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.

How Much Energy Will We Need In The Future?

Micro

bia

l fuel ce

ll Bru

ce E

. Log

an

The Pe

nn

sylv

an

ia S

tate

Univ

ersity

Pub Jo

hn W

iley .

Inc., H

ob

oke

n, N

ew

Jerse

y (2

00

7)

.

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 renewable energy resources, 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

http://en.wikipedia.org/wiki/Barrel_of_oil_equivalent



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).

http://www.eia.doe.gov/cabs/Iran/Background.html

Microbial Fuel Cells (MFCs) – An Introduction

• 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

A Traditional MFC

Chemistry of MFC: Anode Chemistry of MFC: Cathode

MFC Components:

Oxidation –reduction reaction

Substrate : Acetate TEA: Oxygen

Substrate : Glucose TEA: Ferricyanide

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

Micro

bia

l fuel ce

ll Bru

ce E

. Logan T

he Pe

nnsy

lvania

Sta

te

Univ

ersity

Pub Jo

hn W

iley . In

c., Hoboke

n, N

ew

Jerse

y (2

007)

.

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


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)

Continuous- Single-ChamberDesigns

Tubular MFC With Inner Cathode Compartment

Microbial fuel cells: novel biotechnology for energy generation Korneel Rabaey and Willy Verstraete. TRENDS in Biotechnology Vol.23 No.6 June (2005).

• 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).

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:ferricyanideMicrobial fuel cell Bruce E. Logan The Pennsylvania State UniversityPub John

Wiley . Inc., Hoboken, New Jersey (2007).

Mechanisms Of Electron Transfer

• Direct contact through outer-membrane proteins.

• Diffusion of soluble electron shuttles.• Dlectron transport through solid

components of the extracellular biofilm matrix.

A kin

etic p

ersp

ectiv

e o

n e

xtra

cellu

lar e

lectro

n tra

nsfe

r by a

nod

e-re

spirin

g b

acte

ria /C

´ esa

r I. To

rres, A

ndre

w K

ato

Marcu

s, Hyung-S

ool Le

e, P

rath

ap Pa

ram

esw

ara

n, R

osa

Kra

jmaln

ik-B

row

n &

Bru

ce E

. Rittm

ann./FE

MS

Micro

bio

l Rev 3

4 (2

01

0) 3

–17

• 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.

Mechanisms Of Electron Transfer

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

• The solid conductive matrix is likely to act as a semi-conductor (10-6mS /cm<k<106 mS/cm) rather than as a conductor.


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 losses are due to energy lost (as heat) :

Activation Overpotential

• 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)

The intracellular potential :

Edonor-EOM

The EET potential loss : EOM-

EinterfaceThe electrode interface

reaction potential loss : Einterface-

Eanode Overall anode potential

losses

Edonor-Eanode


Voltage losses due to bacterial metabolism

1) Substrate utilization : electrons are transferred from the

electron donor (Edonor) to intracellular reducing power (NADH).

2) Extracellular electron production : ARB have produced the reduced intracellular carrier (NADH), they initiate electron flow through the electron transport chain until the electrons reach membrane-bound cytochromes (ηOM), resulting in a potential loss.

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.

Schematic of processes involved in intracellular potential losses.

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)


• Depending on the characteristic of the solid conductive matrix, its conductivity could be modeled using various equations that describe conductors and semi-conductors (Seeger, 1997).

• We can use Ohm’s Law:

Kbio : the conductivity of the solid conductive matrix (Ω^-1 L^-1)`

Solid conductive matrix mechanism (EOM-Einterface)


Schematic of three EET mechanisms used

(a) direct electron transfer,

(b) electron shuttles, (c) solid conductive

mechanism. 1)substrate

utilization 2) electron

production 3a) electron shuttle

transport between ARB and the electrode

3b) electron transport across a solid conductive matrix;

4) interface electron transfer to the electrode.

kin

etic p

ersp

ectiv

e o

n e

xtra

cellu

lar e

lectro

n tra

nsfe

r by a

nod

e-re

spirA

ing b

acte

ria /C

´ esa

r I. Torre

s, And

rew

Kato

Marcu

s, Hyu

ng

-Sool Le

e,

Pra

thap

Para

mesw

ara

n, R

osa

Kra

jmaln

ik-B

row

n &

Bru

ce E

. Rittm

an

n./FE

MS

Micro

bio

l Rev 3

4 (2

01

0) 3

–17

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

• Electrical resistances of the electrodes• Electrolyte • Membrane They are important at higher current levels.• A resistance of only 15 Ω causes a potential loss

of 150 mV at a current of 10 mA, a loss not to be neglected.

• Reducing electrode spacing.• Choosing membranes or electrode coatings with

low resistances.• Ensuring good contacts between the circuit and

electrodes Increasing solution conductivity and buffering capacity.

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)/


?

But wait… There’s More!

?

?

?

Thank you for your time, and interest in microbial fuel cells!

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).


• 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.


• 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)


• 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.


• 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


• 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.

The Butler – Volmer equation describes the final potential loss

for all EET mechanisms 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.


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

http://en.wikipedia.org/wiki/SI

http://en.wikipedia.org/wiki/Siemens_(unit)

http://en.wikipedia.org/wiki/Ohm

bioreactor design. oil will not appreciably run out for at least 100 years or more, demand for oil...

Documents

costs of energy

energy environment

increasing energy needs

low price of energy

microbial fuel cells

karolien vanbroekhoven

bioreactor design slide

new jersey