Microbial Fuel Cells

1
Microbial Fuel Cells

• And You!

2
What are MFCs?

• MFCs are bioelectrical devices that harness the
  natural metabolisms of microbes to produce
  electrical power directly from organic material

3
MFC Basics
Oxygen Poor
Oxygen Rich
4
Key Players
Mr. Clean (aka Shewanella)
The Iron-Breather (aka Geobacter)
1um

1um
5
Key Players
Mr. Clean (aka Shewanella)
The Iron-Breather (aka Geobacter)
1um

1um
Electron Transfer Mechanisms

• Direct Transfer

• Electron Shuttling

• Nanowires

6
Key Players
Mr. Clean (aka Shewanella)
The Iron-Breather (aka Geobacter)
1um

1um
Electron Transfer Mechanisms

• Direct Transfer

• Electron Shuttling

• Nanowires

7
Respiration
OC
H2S
cell
CO2
SO4--
8
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

9
Anaerobic Microbial Food Chain
10
Applications
11
Soil-based MFCs
12
The MudWatt
Food
13
The MudWatt
14
MudWatt Steps

• Make Fuel
• MudWatt Construction
• Monitor
• Submit Data

15
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)

16
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)

17
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 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)
Nob 1 Blinker Nob 2 100 Nob 3 500 Nob 4
1000 Nob 5 5000 Nob 6 10,000
18
MudWatt Steps
4) Submit Data

• Enter the data youve 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!