Microbial Fuel Cell of Science!!!





Introduction: Microbial Fuel Cell of Science!!!

About: Bill Nye the Science guy is my Hero... that and Bear Grylls...would be cool if they combined to become Bear Nye the Wilderscience Guy using science and technology to drink his own pee.

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


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. 


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!


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98 Discussions

Increasing surface area of cathode may help. a metal plate with one side touches the water surface and the other expose to air.


Question 7 days ago

are all the agar(2 plates) at the top?

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.


1 year 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

2 replies

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.

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.

Why the little blue fish???

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?

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?

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!

How long is the barrier good for? Does the salt eventually get dispersed into the water?

waow cool! produce electricity and the fish can still life :)

Could be possible to "layer cake" them ?

agar -------

muck -----

agar ------

muck -----

this could be augment the electricity ?


2 years ago

I was doing some research on the subject and this is what I came across:

The first step requires the removal of electrons from some source of organic matter (oxidation), and the second step consists of giving those electrons to something that will accept them (reduction), such as oxygen or nitrate

So I know that the first step (oxidation) comes from the muck. Yet it does not seem that reduction is visible in this fuel cell. Could someone elaborate. Because I can't find the second step anywhere. Thanks!

My source: http://www.research.psu.edu/capabilities/documents/MFC_QandA.pdf

2 replies

Look, bro! the reduction actually occurs at the anode surface where it receives the electrons from the bacterial cells or whatever in the mud. The anode receives the electrons found in the mud, the protons passes through the agar-salt to neutralize for charges in both compartments to be received by an electron acceptor, which is oxygen in the demonstrated cell, as water is open to air, thus forming water molecules.

Hey, I was wondering if you could use compost instead of muck and I doubled the amount of ingredients for the PEM. Would it work to just stick tin foil in the pem and then stick that in the middle of my compost bin an have the other electrode in another part of my pile? Thanks!!!!

I'm having a lot of trouble making the PEM solidify, any suggestions?