Introduction: Microbial Fuel Cell of Science!!!
Fuel cell that harvests electrons from the bacteria in mud! And ELECTRons mean ELECTRicity....you get me?
The cell also makes a great habitat for a beta fish... The bacteria decompose the fish poop adding to the cell's fuel and keeping the water clean!
Step 1: Get Some MUCK!
"MUCK" is actually the correct term for soil from Wetlands .... I LOVE WETLANDS!
Muck has all kinds of awesome bacteria, one of which is Geobacter, it produces electrons as part of its cellular digestion!
Step 2: Prepare the Proton Exchange Membrane
75g salt. 200ml water. 5 grams agar or gelatin. Bring to boil. Petri dish. Fridge. Done.
The bacteria produce hydrogen IONS (an ion is an atom that has lost electrons)...a hydrogen ATOM is nothing but a proton and an electron buzzing around it...its like if the Earth was a proton and the moon was an electron...take away the moon....er I mean the electron and all you are left with is a single PROTON aka a hydrogen ION
The PEM as they say allows protons through it and recombine with oxygen and the electrons to form a circuit and H20 as a byproduct.
Step 3: Make Electrodes
PREPARE THE ANODE (-)
Cut up strips of window screen and fold them into a square.
Google how to make "char cloth"....normally its made by survivalists to act as tinder for fire making but the high carbon content will make the bacteria grow and exchange their electrons to the window screen wire! Wrap the screen around a thick mat of carbon cloth. You can also just strip the insulation off the black wire and wrap the copper inner wires around a thick mat of char cloth if you don't have window screen or alligator clips.
PREPARE THE CATHODE (+)
Strip the red wire's insulation back to expose the copper wire's "dendrites" or "feelers" as I like to call them.
Step 4: Put It All Together
- Fill the Beaker with MUCK and the anode (make sure the anode is covered on top and bottom)
- Put the PEM gel mold on top
- Fill up gently with water
- Put cathode in water (half in half out..see pix)
BOOM! Electricity! After a few days you can watch the voltage increase as more bacteria grow on the anode!
Right now I'm experimenting with "charge pump circuits" to bring the voltage up from 500-600mv to 3 volts!
SCIENCE!!!!

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104 Comments
10 years ago on Introduction
Voltage up to 725mV and counting!
Reply 6 years ago
Sir how to glow led from mfc
Reply 8 years ago on Introduction
Increasing surface area of cathode may help. a metal plate with one side touches the water surface and the other expose to air.
6 years ago
I make Proton exchange membrane by gelatin but it fails but I don't know why can you tell me about another recipe to make it, please? or how to make a successful one?
Reply 3 years ago
The difference between activating them is important if you want to use
gelatin instead of agar. Gelatin is made of proteins and peptides and agar is a
polysaccharide.
Gelatin should not be boiled, because it breaks down. Agar needs 95 deg C to
dissolve, so usually it is simply boiled. This means, that if you are using
gelatin, follow the box instructions (3/4 boiling water to ¼ cold water).
Question 4 years ago
How would you measure the electrical output. What would you connect the voltmeter to?
Question 4 years ago on Step 4
How would you measure the electrical output. What would you connect the voltmeter to?
Question 4 years ago on Step 4
what is your materials list, and would the cathode be just a wire?
4 years ago
How do you store the energy made by the MFC?
Question 4 years ago
Could you please tell me how we know for sure that this is indeed microbes at work and not a galvanic cell formed by the metals used?
Question 5 years ago on Introduction
what if we dont want to put the water with the fish would we need to put something on top of the agar?
6 years ago
I quite like your take on the project. I just don't get the role of the PEM: Other projects don't use one, they just use a cylinder that is high enough to ensure anoxic conditions in the bottom. I guess the PEM helps keep the mud separated from the water, but if I don't want fish in the water and instead use plants, I could just top off the mud with some soil for the plants, or am I wrong? Also, are you worried about building a galvanic cell between the steel window mesh and the copper electrode? There is enough salt in the solution to drive a simple battery.
6 years ago
Good day
We have build single chamber fuel cells using stainless steel mesh as anodes and copper as cathode. We also used compost mixed with water instead of muck.
Begin voltage reading is very high and good but within a day it decreases and just keep on decreasing. What are we dong wrong
Reply 6 years ago
You build a galvanic cell. If your electrode materials are not identical, you will build a galvanic cell that just dissolves one of the two metals into the solution while creating a current. If you use metal for the cell, use the same metal on both ends to really only measure biological activity.
Reply 6 years ago
My first guess is that there is not very much that is readily digestible for the relevant bacteria in compost as compared to muck.
What we need to do is run some experiments on different feedstocks.
6 years ago
Why the little blue fish???
6 years ago
The saltiness has me concerned about using this with actual fish. Are you using a betta in this picture because they can stand the saltiness?
6 years ago
I am designing a project for camp students and I was wondering if I could reuse the anode for the projects. I am assuming a new char cloth needs to be used for every project, but can I reuse the window screen? And also what metal should the window screen be made out of? Thank you for your help!
6 years ago
How long is the barrier good for? Does the salt eventually get dispersed into the water?
6 years ago
waow cool! produce electricity and the fish can still life :)