Microbial Fuel Cell: A new device for renewable energy and wastewater treatment

Hung-Thuan Tran and Dae-Hee Ahn

Division of Environmental Engineering & Biotechnology

MYONGJI UNIVERSITY, Natural Science Campus

Yongin City, South of Korea

May, 31st, 2006

NACENTECH, HANOI, VIETNAM

Layout of Talk

! Global status- Energy challenge

- Environmental problem

! A little background on Fuel Cell

! A selective review on Microbial Fuel Cell- Biofuel Cell & Microbial Fuel Cell (MFC)?

- How does MFC work?

- Why is MFC such a HOT topic?

! Perspectives of MFC & Summary

Global Energy & Environmental Impacts! Conventional or Non-renewable sources

- 90% of world’s energy is supplied by fossil fuels (Oil, coal, gas)

- Non-sustainable

- Negative environmental impacts

Oil priceEnvironmental impacts- Air pollution - Ecosystem destruction- Disposal of hazard wastes

0

50

100

150

200

250

300

350

2001 2011 2020

Coal Oil N. GasHydro Nuclear RNE

M TOE (US DOE/EIA-0484, 2002)

“Energy is the single most critical challenge facing humanity”

- Nobel Prize Richard Smalley, 2003

“Energy generation and waste disposal are two key challenges in the quest for sustainable

societies”

- Fritz Scholz & Uwe Schroder,Nat. Biotech. 2003, 21(10)

Fuel Cell Basic principles

Hyundai Signs Deal with IFC to Build DemonstratorH2 Fuel Cell SUVs`

Activation energy

Fuel + Oxidant Reaction products + Energy

Source: 조은애, KIST (2005)

How it works?

• Related to battery: both convert chemical energy into electricity

• Battery: the chemical energy has to be stored beforehand

• FC only operates when it is supplied from external sources

• Fundamental mechanism: inverse water hydrolysis reaction

Anode: 2H 2 → 4H+ + 4e-

Cathode:

4e - + 4H + + O 2 → 2H 2O

Net reaction:

2H2 + O2 " 2H2O + Energy

PEM FC

Type of Fuel Cell

• Phosphoric Acid (160-200oC)

• Proton Exchange Membrane (80-100oC)

• Molten Carbonate (600-700oC)

• Solid Oxide (900-1000oC)

• Alkaline (60-100oC)

• DMFC (60-120oC)

• Regenerative Fuel Cell

Biofuel Cell! Biofuel cells copy nature’s solutions

to energy generation!, says Yakhmi!

! A device that converts the chemical energy into the form of electricity through catalytic activity of biomaterials!

Microbial corrosion

Half-biofuel cell• Enzyme-based biofuel cell

(Enzyme Fuel Cell)

• Microbial-based biofuel cell (Microbial Fuel Cell, MFC)

R.A. Bullen et al., Biosens. Bioelectron. 21 (2006)

Microbial Fuel Cell What is it?

A Microbial Fuel Cell is a mimic of a biological system, in which bacteria do not transfer

electrons to their natural electron acceptor but use an electrode in stead

This creates the opportunity to generate electricity directly from substrate

The working principle

Glucose

NAD+

NADH

NAD+

CO2

MEDred

MEDox

H+ H+

O2

H2O

e-e-

e- e-

BacteriumA

node

Cat

hode

Ion-permeable membraneTerminal electron shuttle

H+

Substrate is metabolized by bacteria, which transfer the gained electrons to the anode

(CH2O)n + nH2O

nCO2 + 4nH+

+4ne-

Electricity production

Big question is arising…!!!

Electron Transfer to Extracellular Electron Acceptors Such as Metals and Electrodes is Fundamentally Different than the Reduction of Commonly

Considered Soluble Electron Acceptors

O2, NO3, SO4,…

Reduction at inner membrane or cytoplasm

???

Fe(III)Fe(II)

How e- can transfer from MO to electrode?

! Mediated electron transfer:

substrate + mediatorO product + mediatorR

mediatorR mediatorO + electrons

MO

anode

! Direct electron transfer:

substrate product + (membrane_cyt-c)

(membrane_cyt-c) (membrane_cyt-c) + electrons

via microbial nanowires, currently

MO

anode_

_

! Direct-like electron transfer:

Self-mediated electron transfer by biofilm bacteria

Why cytochrome?

How microbial nanowire looks like?

Gemma Reguera et al., NATURE Vol 435, 2005, pp. 1098-1101

Self-mediated electron transfer

K. R A B A E Y et al., Environ. Sci. Technol. 2005, 39, 3401-3408

MFC generation

# Mediators: hydrophobic, Quinones..toxic to microorganisms

# No long-term operation# Single strain (limited substrate utility)

# Mediators: benzyl viologen, thionoine2, 6-dichlorophenolindophenol methylene blue, …

Med

iato

r-le

ss

MFC

# Novel technology

# Mediator-less system # If mixed culture,

wide spectrum of substrate utility# Long-term operation # Economically viable (energy)

Conv

entio

nal

MFC

(w

/Med

iato

r)

Look inside MFC again!

Energy available for electricity generation

K. Rabaey and W. Verstraete, TRENDS in Biotechnology Vol.23 No.6, 2005

Who are EAB?

EAB = Electrochemically Active Bacteria$ They have ability to transfer electrons from oxidized fuel

(substrate) to water-insoluble materials (electrode) without a mediator

$ To date, many species are known, including Aeromonashydrophilia, Clostridium Butyricum, Desulfoblbus propionicus, Enteroccus gallinarum, Geobacter sulfurreducens, Rhodofoferaxferrireducens and Shewanella putrefaciens

$ Interestingly, in the MFC system, growth and metabolism of EAB was dependent on the presence of the active anode - in essence, it served as the electron acceptor for growth and metabolism

$ To this end, single strains, as well as bacterial consortia have been enriched on anodes of MFCs

I. S. Chang et al., J. Microbiol. Biotechnol. (2006), 16(2), 163–177

Emerging opportunities of MFC

BOD sensorsB

ody

fluid

bat

terie

s A robot with stomach

Power mobile deviceSediment electricity “Waiter, one sugar cube for my

coffee, and one for my mobile phone…”

The order from customers in restaurant

Wireless sensor

MFC is such HOT issue?

MFC on cover of ES&T (Vol.40-4, Feb.2006)

MFC on cover of Science News(Vol.169-5, Feb.2006)

FutureEnvironmental Technology is not only a treatment process, but also energy recovery process.

Current Environmental Technology is a treatment process.

EnvironmentalWaste

Paradigm Shift of Environ. Tech.

from disposing of waste to using it

Energy from wastewater?

Guri Municipal Wastewater Treatment Plant, Korea

Taken by Hung Thuan Tran

Energy Costs?

5-7% of electricity used in USA is for water & wastewater treatment, says Logan

…???

Wastewater is not only consisted

of pollutants but also has potential

sources of renewable energy

Electricity out of biomass

$ Direct conversion of substrate (waste) to current$ No high temperature required$ No gas treatments needed

$ Can work with low strength

1 kg Sugar

~4.4 kWh

0.5 m3 biogas

(mainly CH4)

1 kWh 3 kWh

Electricity heat

1 kg Sugar Up to 4.4 kWh

~4.4 kWh electricity

$ Sustainable energy systems$ Energy efficient wastewater treatment

• Technology needed

• Existing: Anaerobic digestion$ Generation of methane$ 35% recovery as electricity$ Not suitable for low strength

• Microbial Fuel Cell provide

MFC construction & operation in WWTTubular-type MFCUF-MFC/w

membrane

Washington Uni.

in St. Louis

UF-MFCmembrane-less

KISTGhent Uni.

Single chamber-Air cathode type MFC

Stacked-type MFC

Ghent Uni.

Two chamber MFC

TNO Envi., Energy & Process Innovation, The Netherlands

Penn State Uni., US

Demonstrations of MFC

KIST, Korea PSU, United State

Perspectives

• So far, MFCs have been only used for treating organics in wastewater

• Cathode materials should be p-group metal for electrochemical cathodic reaction

• How about bio-electrochemical cathodic reaction?

• Nutrient removal in MFC?

If possible….!!!

NOx-

Bacterium (or biofilm)

-

-

Electrode (cathode)

Electron

N2↑

This creates the opportunity for Simultaneous Organic and Nitrogen Removal from Wastewater

The application niche

• Waste processes (material has negative value)$ Priority: removal C, N and P$ Sub-priority: generation of electricity

energy efficient treatment

• Qualitative processes (material has positive value)

$ Priority: generation of power$ Sub-priority: safety and sustainability

sustainable and safe electricity generation

Summary

1

2

3

4

5

would be a completely new approach to WWTwould be a completely new approach to WWT

for controlling bacterial metabolic pathways ?for controlling bacterial metabolic pathways ?

as a good candidate for Nutrient removal ?as a good candidate for Nutrient removal ?

as a new concept of Environ. Energy Tech.as a new concept of Environ. Energy Tech.

is still in early state of developmentis still in early state of development

End of Presentation&

Thank You for Your Attention!!!