Introduction: Microbial Fuel Cell of Science!!!

Picture of Microbial Fuel Cell of Science!!!

Fuel cell that harvests electrons from the bacteria in mud! And ELECTRons mean 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!

Picture of 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

Picture of 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 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

Picture of 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

Picture of 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!



drdan152 (author)2013-08-18

Voltage up to 725mV and counting!

LavanyaU (author)drdan1522017-01-19

Sir how to glow led from mfc

CorneliusC1 (author)drdan1522015-06-14

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

ohyouhere (author)2017-07-19

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.

JonkT (author)2017-03-06

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

ohyouhere (author)JonkT2017-07-19

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.

Hairyloon (author)JonkT2017-06-12

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.

DEEJAY246 (author)2017-07-08

Why the little blue fish???

merna tamer (author)2017-04-19

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?

whitsona (author)2017-03-03

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?

PranavR21 (author)2017-01-27

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!

whitsona (author)2016-10-21

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

rimbow46 (author)2016-10-06

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

MaximeB19 (author)2016-05-16

Could be possible to "layer cake" them ?

agar -------

muck -----

agar ------

muck -----

this could be augment the electricity ?

Murad_ (author)2016-02-07

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:

MarMK (author)Murad_2016-04-04

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.

Murad_ (author)MarMK2016-04-14


gmathesen (author)2016-03-26

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!!!!

Jen0_0nn (author)2016-03-22

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

gmathesen (author)Jen0_0nn2016-03-26

I you have to mix all the ingredients together and boil it then cool it down in the frige. If it keeps melting when you set it out on the counter, then make sure that you are using agar (can get it from most health food stores as a vegan gelatin) and not gelatin as gelatin melts if it gets over 20 C. Hope this helps. I just made mine and it seems to have worked fine.

GavinEvjenth (author)Jen0_0nn2016-03-22

so am i can i have some help with this too?

GavinEvjenth (author)2016-03-13

Thanks for the fast response, I am doing a science project on this and I'm SOOOOOO excited. Do you think this would work as a habitat during the experiment for my pet gold fish and my other types of fish that I have? Also great inscrutable! :)

drdan152 (author)GavinEvjenth2016-03-14

I'm so happy my instructable is exciting! Isn't science AWESOME!!! And for sure your goldfish could live in the fuel cell because the water and muck are all from typical fresh water habitats that would support fresh water fish! As a neat experiment you could buy some Ph and other water test strips from a pet store and test the fuel cells water quality at the start and a few days after its running to see if the acid levels go up or something before you put a fish in..... Also you can test how doing water changes (to keep the fishtank clean) affect the voltage! There are so many variables and who knows what you might discover!

Zami47 made it! (author)2016-02-14

It gave me around 550mV

drdan152 (author)Zami472016-03-13

wow! Great job!!

GavinEvjenth (author)2016-03-12

does it have to be muck or can it be sand or mud?

drdan152 (author)GavinEvjenth2016-03-13

Hey! It prob won't work with sand..... Mud may work but muck from a wet land like a pond or marsh or bog works because it has the GEOBACTER bacteria in it! Ps the fish is only to show how safe the fuel cell is and natural..... It doesn't need the fish!

GavinEvjenth (author)2016-03-13

please respond fast if possible! Thanks

GavinEvjenth (author)2016-03-12

Does this experiment only work with beta fish or does this work with all types of species of fish?

kenabena12 (author)2016-01-27

I'm building this for my science fair assignment but my teacher wants to know what is the size of the PEM, because it looks fairly large in the picture but, if I am correct, judging by the measurements to make the Proton Exchange Membrane it isn't that big. Am I correct? @drdan152

drdan152 (author)kenabena122016-01-28

Hey! Cool! Your right it's not that big..... I just used a "Petri dish" filled with salt and gelatin...... Jello with extra salt added should work ok too! Really the principal is that there should be a layer of muck then a PEM on top of that then water! So how ever you accomplish that...... It's up to you!

Chazman1992 (author)2013-09-22

What has been the most efficient anode design? Screen mesh? Wires to the cloth? If so how? Flat? Rolled! Max surface area?

drdan152 (author)Chazman19922014-04-04

flat and max surface area!!!

kunjan94 (author)drdan1522016-01-06

Graphite is better as electrode.

kunjan94 (author)drdan1522016-01-06

Graphite is better as electrode.

R2D2J2B2 (author)2015-01-28

Thanks for the great instructions! I'm doing this for my science fair project, and the voltage from my first attempt is decreasing daily rather than increasing. Any suggestions?

kunjan94 (author)R2D2J2B22016-01-06

its because bacteria need food for their life cycle, try adding glucose or other sugars with it.

BlahBlahJooo (author)2015-07-04

Um I'm confused with the proton exchange membrane. Do you have to freeze it?

kunjan94 (author)BlahBlahJooo2016-01-06

yes you do have to freeze (solidify) it.

SHOE0007 (author)2015-12-06

In a anerobic enviroment it started reducing the bacteria and clogged the probe voltage dropped to 560 mV.

SHOE0007 made it! (author)2015-12-06

Here is a small portable bioreactor made from a broth of 1 million cultures of lactobacilus retuni which converts glucose into lactic acid, citric acid, succinic acid and other acids. The ph drops and this increases the acidity. The probes are copper and stainless steel. The voltage measured was 706 mA.

yobo520 (author)2015-11-23

Were you able to eventually power an led and design the charge pump circuit. If so could you send pictures and instructions on how you did so. I'm designing one for a science project and my goal is to try and power a led light.

fumunda2jp made it! (author)2015-11-17

My son just made one today for science project. Its been a steady 950mV for the first 6 hours. Maybe we will get over a volt??? Cool project.

drdan152 (author)fumunda2jp2015-11-19

Wow! It looks great! Nice job! Glad to hear people have fun making the projects!

holymoses (author)2015-07-22


I see cruelty to animals!

Except this is a plastic fish but then still it is idiotic to publish this way!

souravsharma1768 (author)2014-10-28

What do you mean by "cover the anode from top and bottom".

gabedc (author)2013-09-29

Hey! I was looking at this and plan to wire up a bunch of them for higher voltages, but how does this beta fish survive? What does it feed off of?

Thanks for your help!

drdan152 (author)gabedc2014-04-04

The cell is a totally harmless (although small) aquarium.....totally PH balanced and the bacteria has nitrogen fixing bacteria that help keep the water clean! Just feed the fish like you normally would and water changes etc.

goodiesohhi (author)gabedc2013-10-20

Beta pellets..... Duh..
What else?

goodiesohhi (author)2013-10-20

What step does the Beta come in?

About This Instructable




Bio: 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 ... More »
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