Microbial Fuel Cells
And You!
What are MFCs?
o
MFCs are bioelectrical devices that harness the natural
metabolisms of microbes to produce electrical power directly
from organic material
MFC Basics
Oxygen
Poor
Oxygen
Rich
Key Players
Mr. Clean
(aka Shewanella)
The Iron-Breather
(aka Geobacter)
1um
1um
Key Players
Mr. Clean
(aka Shewanella)
The Iron-Breather
(aka Geobacter)
1um
1um
Electron Transfer Mechanisms:
o Direct Transfer
o Electron Shuttling
o Nanowires
Key Players
Mr. Clean
(aka Shewanella)
The Iron-Breather
(aka Geobacter)
1um
1um
Electron Transfer Mechanisms:
o Direct Transfer
o Electron Shuttling
o Nanowires
Respiration
OC
H2S
cell
CO2
SO4--
Redox Gradients


Max potential ~1.2 V (= potential
difference between NADH and
O2)
If terminal e- acceptor has lower
potential than O2:


Bacteria gain less ATP per mole
organic carbon oxidized
Remaining energy is available to be
used in MFC
Anaerobic Microbial Food Chain
Macromolecules
Monom ers
Fer men tin g Bacteria
H 2 + CO 2
Acetate
Acids, Alcohols
Fer men tin g
H 2 + CO 2
Fer men ters Acetogen s
Acetogens
Acetate
H 2 + CO 2
Methanogens
Acetate
Ac
Acetogens
Acetate
Methanogens
CH4 + CO 2
Southern We tlands
Warm ing
Nort
Applications
Soil-based MFCs
The MudWatt
+Food
The MudWatt
MudWatt Steps
1)
2)
3)
4)
Make Fuel
MudWatt Construction
Monitor
Submit Data
MudWatt Steps
1) Make Fuel


Put ~3 cups of soil in bowl
(Optional) Add mystery ingredient
Hint: if your mystery ingredient is liquid, add just enough to make the soil “cookie
dough” consistency


Add water until “cookie dough” consistency
Record your ingredients (and volume fraction of secret ingredient if
one was used)
MudWatt Steps
2) Construct MudWatt








Attach electrodes to dome lid (through donut disk)
Attach ruler sticker to the side of vessel
Put mud in vessel up to 1cm. Pat smooth
Place in Anode (make sure there are no air bubbles)
Put in more soil up to 4 cm
Place in Cathode
Let rest for 2min
Decant liquid if needed (Cathode cannot be submerged)
MudWatt Steps
3) Monitor (Perform this technique every week)

S1) Switch the electronics panel to Open Circuit mode by
turning all switches off.

S2) After 30 minutes, check the voltage across the two
leads using any voltmeter (black to “-“, and red to “+”).
Record the voltage and the resistance. (the resistance is infinite
The resistance for each Nob is outlined
as follows (in Ohms):
under “Open Circuit” mode)

S3) Repeat S2 for the 5 different resistances provided on
the electronics panel. Turn only one Nob on at a time.
Nob #1= Blinker
Nob #2 = 100
Nob #3 = 500
Nob #4 = 1000
Nob #5 = 5000
Nob #6 = 10,000
MudWatt Steps
4) Submit Data

Enter the data you’ve collected at
www.keegotech.com/community/datashare
Thank You!
With the data collected and submitted by you and your fellow Keegoites, we
hope to uncover trends and peculiar behaviors of microbial fuel cell technology.
In this way, we aim to catalyze the development of this technology in the hope
that someday MFCs will be a viable option in providing affordable and reliable
energy for those who would benefit greatly from it. Developed by the public,
for the public. All hail the Keegoites!