Microbial Fuel Cells - A Way to Generate Clean Electricity from Waste Water

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Picture of Microbial Fuel Cells - A Way to Generate Clean Electricity from Waste Water

Over 1.5 billion people in the world have no access to electricity. That means 1 out of 5 people are forced to live without something that a majority of the world takes for granted everyday! Without electricity, these people are unable to refrigerate food/medicine, have a guaranteed light source, or even have access to safe heating methods. In fact, according to a joint report of the United Nations Development Program and the World Health Organization report, 2 million people die unnecessarily each year due to inhaling the indoor smoke caused from burning coal, crop residue, wood, and even dung for heating and cooking purposes. This is precisely the reason why we want to change this. Our goal is to find an easy and affordable method to supply energy to these 1.5 billion people. We hope to mainly use items that would be accessible or could be easily supplied to persons in need.

Step 1: Summary

Lack of electricity in many less developed countries prompted us to perform this project to submit to the Google Science Fair. We created a microbial fuel cell (MFC) using easily accessible and cheap materials. The MFC utilized waste water and lactobacillus to create hydrogen peroxide, which when forced through a proton exchange membrane, created electricity cleanly and cheaply. The proton exchange membrane separated the hydrogen peroxide molecules and allowed only hydrogen ions to pass. Free electrons went through a carbon rod anode and was utilized as electricity.

The MFC was set up in a garage and used for 5 days. A multimeter was attached to the anode and cathodes in order to test and record the electrical output of the MFC. The MFC consisted of an anode and cathode chamber. The anode chamber was filled with 'waste water' or dirty pond water, and yogurt containing lactobacillus. It was attached to the cathode chamber using PVC segments with the proton exchange membrane in it. The cathode chamber was then filled with tap water and a phosphate buffer to maintain pH levels. Our results demonstrated the potential effectiveness of MFCs. Additional funding, research and investigation would allow for greater practicality in developing nations.

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This is awesome!

Very cool concept!

thassaj1 year ago

Impressive! There are ways of getting the voltage higher - one way being of course to put say 17 of these cells in series. Another way would be to use one of those little low voltage ICs that can take voltage levels like 0.3 volts and multiply it up. Somebody help us out here: which ICs are the low voltage multipliers? They can take low voltages from things like thermocouples and make them useful. You would still need a few cells to get useful amounts of power, but it might be that you can trickle charge a 5V battery all day long and end up with a light that works at night so that students can study by it.

check out dx.com 4 thos buck converters nice little gadgets they are!!

Texas Instruments offers energy harvesting ICs such as this one:


It can operate from voltages as low as 80mV and includes circuitry for battery management and charging.

Hope this helps :)

rusty13001 year ago

Hey good on you guys for thinking out of the box. It's guys like you that will drive innovation of tomorrow. Well Done

It's kids like this that make me less worried about the future.

ian.gallinger4 months ago

lol i live right next to mlhs

even beat them in football

i wanna ask something, how do microba or bacteria produce energy in MFC? Anyone? Thanks before :)

ccpro147 months ago

cool one man but i dont understand the building concept

Excellent and thank you and i am using this experiment to science exibition

jferkans1 year ago
Holy genius... I wish I had a brain like that and the ingenuity you do
luillo1251 year ago

I read some papers on this topic. Very interesting and novel topic, you can also try using sewage or "dirty" water as a carbon source for the bacteria, and also adding a middle chamber between the anode and cathode to also perform water desalination, also the H2 produce can be gathered and used as a form to produce H2. Simply awesome technology

shomas1 year ago

Because power=volts ^2/resistance, At .3 volts and 80 ohms this microbial battery cell produced .3^2*/80=.00120125 watts an hour or 1.20125 milliwatt hours. A joule being a watt second (a unit of energy) means that you produced about 97.2 joules a day.

As the cell pretty much "settled down" for consistent results after a couple days, maybe it would have been interesting to vary the load at the end of the test. Although I strongly suspect that the anode and cathode surface area is proportionate to its power capacity, maybe a different load will result in more or less power produced.

manuka1 year ago

Profound apologies if my earlier comment seemed a tad unsupportive to the MFC researchers. I've had extensive Science Fair experiences during a lengthy academic career, & the comment was essentially intended as peer review. It's better that issues & claims are addressed early on rather than at judging time!

Direct communication has instead now been made with the " gang of 3 ".

robosilo1 year ago

Great work guys. Do you have any links providing more info on how chicken eggs are used to make ion exchange membranes?

bkonfuzius1 year ago

Very nice work & you really got me interested

but for instructables, a bit more of a step by step on the methods would be nice!

and as you guys wrote that you want to be all big researchers one day, I recommend giving some refrences to the research you based your experiment on (MFCs in general, usage of lactobacillus for MFCs)

and for further research: dirt water and yogurt contain a whole bunch of different microorganisms. if you guys have access to a lab: maybe check out, what type(s) of bacteria were actually dominant in your anode bottle (over time).

manuka1 year ago

I may have missed further details but - as others have also mentioned- the only results found were the VOLTAGES shown below. Produced CURRENT into a load should also have been recorded, as of course it's electrical POWER (= V x I ) that you're after.

In any case I respectfully mention that your voltages are so puny
that little practical work could be done with them...Yoghurt is too
valuable as a food as well!

Perhaps far better for "poor villages" these days are PV (photovoltaic) cells -typically even a dirt cheap solar garden lamp type will produce ~2V at ~30mA in sunshine. And of course sunshine is just what such less developed regions often have in great abundance!

Aside from the valuable LED night lighting or cell phone charging that even tiny PVs can provide, larger PV panels used in the likes of Sahel (sub Saharan) Niger have transformed their rural lifestyle & agriculture by powering deep well water pumps. Refer a lucid study => http://cdn.intechopen.com/pdfs-wm/42485.pdf


Over the course of the experiment, we measured the voltage produced each day:

  • Day 1 - 0.33 V
  • Day 2 - 0.36 V
  • Day 3 - 0.32 V
  • Day 4 - 0.31 V
  • Day 5 - 0.30 V
  • Day 6 - 0.30 V
kasisnu manuka1 year ago

Well, it was an experiment. And they are looking to refine the process. Isn't that worth exploring?

This comment was really nice and constructive. Have a free pro membership.

Thank you! :)

Pro Member :) You have made my day, thanks!

Stop hating on these boys project, no one care about you "puny" comments, they are doing great work!

ASCAS1 year ago

Congrats and great work! You guys should try a joule thief.

ianmcmill1 year ago

This is nice !

Mikel991 year ago

Helping one person isn't a sound economic basis for much....I would leave that out in future.

dproteus1 year ago
What is the current produced? A quick Google says a white LED needs 20mA@5V, so you'll need to get 333mA to light a single LED with this size rig (20mA*5V=100mW, 100mW/0.3V=333mA). So if you get around that much, this could definitely serve to power a small table lamp in a developing country. Think of those keyring flashlights, and that's about how much light you would get, which is impressive from just your local pond scum :)

Firstly an LED NEEDS a certain amount of voltage just to turn on(so .3V will do squat), typically around 1V and can usually operate an LED at 10mA. I'm not sure who on Google told you 20mA@5V but they are woefully wrong. I do want to know how much current is produced however. Very intriguing concept! Cool factor 5/5! Lol

I will certainly admit my analog circuitry knowledge is minimal, but doesn't Ohms Law let you adjust both voltage and current using resistance, so long as you have sufficient power? V=IR, so if I have more current than I need, but not enough voltage, I think I can shift the balance between the two, right?

The source I used for 20mA@5V is. http://www.physicsforums.com/showthread.php?t=476156 which was the first or second result from Google at the time. Like I said, just a quick search. ..

Unfortunately no. Because of the P-doped and N-doped regions of the diode (in this case light emitting diode, LED) a certain amount of potential energy, voltage, must be present in order for the device to function properly. For an average diode this is .7V but for an LED it is significantly more, 1 - 1.5V depending on the color of the LED. Technically Ohm's Law applies to linear devices and because of the PN properties an LED is not linear. This being said, once you account for the required voltage drop of the LED, Ohm's Law works pretty well! Not super precisely but close enough it works! :)

Nice work! Go on! One question you've made some energy-balance or something? Thinking of input-side: one yoghurt, the lactobacil will reproduce to keep the process going? What contained the wastewater that made the reaction going on? Output: The wastewater afterwards is "clean"? Or to be used in something? The pH buffer had to be renewed to get on?
hqmhqm1 year ago

Nice project! It would be good to know the actual power generated. To do this you need to have some kind of resistive load, and measure the current that flows, ideally with several different load resistance values.

You should look up "source resistance" and "Thevenin equivalent resistance".

That is a very simple idea that says you can model most real world voltage or current sources as an ideal current or voltage source connected via a single series or parallel resistor. (note it does not model nonlinear sources)

This may be a good way to characterize the properties of your power source; it's like if you have a AA battery cell, it puts out 1.5 volts under no load, but it has an internal (source) resistance which is what determines the maximum amount of power that can be delivered. If you can find that source resistance, you will know how much power your system can deliver.

triiiiiple1 year ago

project is good but its not easy to find out what and where should be... i would make more siple steps, not one, where is whole construction and the others.

rspellicer1 year ago

Brilliant! Low-buck, low-tech power, what much of the 3rd world needs. Keep experimenting and updating results.

rich_moe1 year ago


While the amount of voltage is low, the potential for generation of "free" electricity is just beginning. I do have to point out one little detail; while in this experiment it was a proof-of-concept, and rather well documented, I didn't see what load was placed on the "generator" other than the multimeter. All in all, very impressive.

tygger2811 year ago

WOW! So, the possibilities really intrigue me! I have two spring fed ponds on a property up in the national forest. I am wondering how this would scale up with a natural water source with an existing ecosystem in place?

Sorry, but I think you would just poison the water.

I suggest you try solar, wind and hydro-electric power.

ar_caver1 year ago

Good start. I bet with a little more effort you could refine both this idea and the instructable.

Ninjabdou1 year ago

Great; this is amazing

neowton1 year ago

Yeaaah @JoshHawley, the most important of the information got it in this tech is the correct measurements of "power" to make a great analysis balance. I invite to Austin Simonson, Frank Zhang, Willy J and everyone who want to make every thing better, in order to get one of the best instructables in the future. Where every world can enjoy the knolewdge acquired.

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