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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)
1um1um
Key Players
o Direct Transfer
o Electron Shuttling
o Nanowires
Electron Transfer Mechanisms:
Mr. Clean(aka Shewanella)
The Iron-Breather(aka Geobacter)
1um1um
Key Players
o Direct Transfer
o Electron Shuttling
o Nanowires
Electron Transfer Mechanisms:
Mr. Clean(aka Shewanella)
The Iron-Breather(aka Geobacter)
1um1um
Respiration
cell
OC
CO2 SO4--
H2S
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
H2 + CO 2
H2 + CO 2
Acetate
AcetateAcetate
Acids, Alcohols
CH4 + CO 2
H2 + CO 2
H2 + CO 2
Acetate
AcetateAcetate
Acids, Alcohols
CH4
Macromolecules MonomersFermenting BacteriaFermen ting Bacteria
MethanogensMethanogens Methanogens
Acetogens AcetogensFermen ters Acetogen s Fermen ters Acetogen s
Southern We tlands Northern We tlandsWa rming
Fig. 1. Simplified model of anaerobic processes in northern (right) and southern wetlands. Acetate is not a precursor of CH4 andaccumulates in the north. The disruption of terminal activities in the north leads to a unique microbial consortium at virtually all
levels including bacteria in the food chain well above the methanogens. Climate warming causes the northern system to convert toone similar to the south where CH4 is derived also from acetate leading to a marked increase in CH4 emissions and a change inbacterial population composition.
Applications
Soil-based MFCs
The MudWatt
+Food
The MudWatt
MudWatt Steps
1) Make Fuel2) MudWatt Construction3) Monitor4) Submit Data
MudWatt Steps
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)
1) Make Fuel
MudWatt Steps
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)
2) Construct MudWatt
MudWatt Steps
3) Monitor (Perform this technique every week)
Nob #1= Blinker Nob #2 = 100Nob #3 = 500Nob #4 = 1000Nob #5 = 5000Nob #6 = 10,000
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 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.
The resistance for each Nob is outlined as follows (in Ohms):
MudWatt Steps
Enter the data you’ve collected at www.keegotech.com/community/datashare
4) Submit Data
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!