MFCs (Microbial Fuel Cells)

RET, Summer 2009

John A. Bogucki

Clay High School

South Bend, Indiana

Microbial Fuel Cells

Use bacteria to convert organic and

inorganic waste materials into electricity

Electrical energy in the form of

electrons are generated by the normal

metabolic activity of the bacteria in

oxidation-reduction reactions

Microbial Fuel Cells: A brief overview

COD

COD

H+

e-

H+ H+

H+

e- e-

e-

O2

O2

H2O

Proton Exchange Membrane

Anode

Anode

Cathode

Cathode

COD =

Organic Matter

Electrochemically-

active biofilm PRODUCE ELECTRICITY WHILE REMOVING ORGANIC MATTER!

MFCs function by

Converting energy available in the

substrate directly into electricity

This is achievable when bacteria switch

from the natural electron acceptor, such

as oxygen or a nitrate, to an insoluble

acceptor, such as the MFC anode

4 Components of an MFC

1. Anode

2. Cathode

3. Electrolyte

4. Proton Exchange

Membrane

1. Anode – negative electrode

Anodophilic bacteria colonize the surface

of the anode and form a “biofilm” on it

They are electrode-reducing organisms

They release electrons to the anode

2. Cathode – positive electrode

• Some MFCs utilize a biotic cathode while others utilize an abiotic cathode.

• Cathodophilic bacteria can colonize the surface of the Cathode and form a “biofilm” on it creating a biocathode

• These are electrode-oxidizing organisms

3. Electrolyte – aqueous solution

For each electron produced, a

proton must be conducted to the

cathode through the electrolyte to

sustain the current

4. Use of a PEM

PEM = Proton Exchange Membrane

• To separate the catholyte from the anolyte

• Keeps chemicals and materials other than

protons from reaching the cathode

MFC Power Generation

Maximizing power generation in MFCs

requires innovative flow patterns and

electrode orientations that minimize

resistance

MFCs have produced up to 1 kW/m3 on a

bench scale, but no one has developed a full

scale system yet.

MFCs are being constructed using a variety of materials and configurations

1. Traditional H-shaped

2. Square or Box type

3. Tubular

4. Other designs

H shaped MFC

Box or Square Type MFC

Tube or Cylindrical MFC

Sulfur Granules &

Graphite Granules

Sulfur Flakes &

Graphite Granules

My Innovative Fuel Cells

Sulfur Granules

Electron Donor

Sulfur Flakes

Electron Donor

Graphite granules

Electron acceptors

Media Pump MFC

Uses of MFCs

1. Waste water treatment

2. Removal of specialized contaminants

(like Perchlorates)

3. Powering Sensors

Advantages of Using Sulfur

1. Creates a bacterial battery

2. Doesn’t need to be constantly

replenished

3. Sulfur is plentiful and inexpensive

Layered Sulfur Based MFC Design

Proton Exchange Membrane

Anode Cathode

Air Sulfur and

Graphite

(PEM)

Sulfur MFC's

0

2

4

6

8

10

0 10 20 30 40 50

time in days

su

lfate

in

mg

/L

MFC-EJ

MFC-BE

BE (Sulfur Flakes) Power

0.0E+00

2.0E-03

4.0E-03

6.0E-03

8.0E-03

1.0E-02

1.2E-02

1.4E-02

0 200 400 600 800

Time (Hours)

Po

wer

(W/m

^3)

BE

EJ (Sulfur Granules) Power

0.0E+00

5.0E-03

1.0E-02

1.5E-02

2.0E-02

2.5E-02

3.0E-02

0 200 400 600 800

Time (Hours)

Po

wer

(W/m

^3)

EJ

Caitlyn Shea

Dr. Robert “Rob” Nerenberg