Introduction: Microbial Fuel Cells - a Way to Generate Clean Electricity From Waste Water

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.

Step 2: A Little Bit About Us

We, Austin Simonson, Frank Zhang, and Willy Ju, are juniors (11th grade) attending Mira Loma High School, located in Sacramento, CA. We all are enrolled in the International Baccalaureate program (aka "IB") and are on our way to getting our IB diplomas next year. We are all taking rigorous courses in the sciences and math to challenge us and to help guide us in pursuing our future career paths. We strive to become the world's next doctors, chemists, and engineers. With our passion for the sciences, we all came together to apply our knowledge in creating a model that the world will be able to appreciate and further apply in society. Our hopes and ambition are that our efforts will someday have an impact on our world in the near future.

While all three of us strive to attend some of the most well known colleges in the US, no matter where we end up attending, our goal will remain the same: to learn as much as we can and to use our knowledge to better the lives of everyone around us. In our free time (whenever we can find some), we like hiking in the outdoors, tinkering, learning new and interesting things, and of course, connecting with our friends on social media.

Step 3: Research

Studies have shown the practical and helpful applications of microbial fuel cells (MFCs). Practically any organic matter such as human, animal, and industrial wastewater, along with sugars, starch, and cellulose, can be used to fuel a MFC to generate electricity. MFCs also have to potential to treat waste water and can be implemented in water treatment plants. With this in mind, we looked at the possibilities of actually building a MFC with easily accessible, cheap, and common materials. Examining the parts of a typical MFC, the materials to build an effective MFC can cost hundreds of dollars. By using cheap, common materials the cost of the materials can be reduced significantly.

How it works: There are two chambers: the anode and the cathode. The anode contains the bacteria (lactobacillus) and organic matter while the cathode contains a phosphate buffer (ph 7.7). The bacterial in the anode will have to undergo anaerobic respiration which requires a void of oxygen in that chamber while the cathode needs to have a presence of oxygen. As the electrons in the anode are oxidized, the electrons are then carried through a wire connected to a carbon rod from the anode to the cathode, reducing the water in the cathode. Hydrogen ions that are produced in the reactions in the anode are also moved from the anode to the cathode through a semi permeable membrane for protons (H+ ions). This creates a electrochemical-chemical gradient which essential allows for the current to flow through the wire.

Step 4: Our Method

Picture of Our Method


The goal of this project was to use easily materials easily accessible in developing nations. To achieve that aim, old 2 liter soda bottles were used as containers, carbon rods used as electrodes, Nafion 117 as the proton exchange membrane (PEM), a phosphate buffer to maintain pH in the cathode chamber, and PVC piping and coupling. Additional materials included hot glue, tape, copper wires, and a multimeter. PEM's may be acquired naturally through chicken eggs, whereas carbon rods are found in non alkaline batteries, thus both essential materials could be acquired in less developed nations. Additionally, any plastic containers, tubes and conductor could be used. Hot glue and tape was used to hold the assembly together, but any adequate material could suffice. Finally, the multimeter was used to test the electricity generated from the Microbial Fuel Cell (MFC), but would be replaced by the target device in actual usage. Finally, the waste water used was dirty pond water taken from a creek, and the cell culture used was lactobacillus, taken from yogurt. In actual use, waste water used may be dirty sewage such as excrement and trash in water. Lactobacillus occurs naturally, especially in many dairy products. A further wide range of bacterium may also be used.


Holes were cut in the same place in both soda bottles, such that a PVC attachment could be placed laterally. The two PVC segments were fed through the holes and secured using tape and hot glue to form a watertight seal. The PEM was stretched over one end of the PVC segment and then both segments were attached to each other using the coupler, thus locking the PEM in place. The Carbon rods were sanded and then soaked in distilled water to increase effectiveness. In the Anode chamber, yogurt and dirty pond water was placed inside. The cathode chamber was filled with freshwater and a 7.7pH phosphate buffer. Finally, carbon rods were placed in both chambers, and attached to wires that lead to the multimeter. The multimeter was checked every 6 hours. A video camera was set to record the multimeter at night using the lowest framerate, no sound, and low resolution, such that we could check the readings in the morning by jumping to the right time.


Setup was kept in a windowless garage over a period of several days where the temperature ranged from (low) 7-9C and (high) 25-28C (13-17 April), as temperature affects the growth of lactobacillus (Siegrist). A catholyte, the phosphate buffer maintained the pH of the Cathode chamber. A small flourescent lamp was turned on next to the setup, which allowed the camera to record, and to to maintain the light level of the setup.

Additional Safety

The waste water was safely disposed of and the anode chamber thoroughly cleaned afterwards. Carbon rods were purchased as chemicals in batteries could potentially have been hazardous to health if not opened correctly.

Step 5: Results

Although this was only done on a small scale, we were able to see some interesting results.

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

As you can see from the data, the most voltage generated was on the second day, although, between day 3 to day 6, the voltage only dropped 0.02 V, showing that this would be a viable source for continuous electricity production, especially when constantly maintained and "fed" (by adding more glucose, organic materials, Lactobacillus, etc. as necessary).

In addition, the voltage could also be increased by linking these "chambers" together in series. From information we just found out, it may also produce more voltage with a zinc electrode on the anode side and a carbon electrode on the cathode side, but we have not yet tested this theory. On a large scale, this has potential to generate hundreds of volts when properly assembled and maintained.


A lot of people have asked about the current. With 80 ohms of external resistance, we were able to achieve a little over 3.1 mA. In addition, remember that this is a crude prototype of what is possible. Remember that wastewater is being used, not clean water, and it is inevitable that wastewater will always be created. This simply is an intermediate step between the production of wastewater and the cleaning of it.It could somewhat easily be implemented in an already constructed wastewater treatment facility. And would have little to no effect on its operation, other than generating electricity.

Step 6: Conclusion


As we see from this information, although the amount of electricity produced is seemingly insignificant when compared to the amount of electricity the world uses in a day, it is a step in the direction of clean energy for all. If this concept was to be implemented on a larger scale, the results would be very significant in helping contribute to the world's energy problems. Even if this only helps out one person, it would be all worth it.

Limitations of the Current Study

As our experiment was conducted on a small scale using materials like plastic bottles, there would definitely be a difference when conducted on a larger scale, which would need to determined and rectified before testing/implementing this concept on a larger scale. Like most any experiment, human error is almost always a contributing factor; over the course of this study, we did our best to keep this error to a minimum. In addition, we only were able to use the Lactobacillus bacterium, which is one of many bacteria that would have been acceptable for this form of energy production.

Recommendations for Further Research

The experiment could be repeated using bacteria that has adequate qualities for this type of energy production to determine if one form is able to generate more electricity. Other electrodes than carbon rods (such as zinc rods) could be used and tested to determine if that will affect the overall energy output.

As this is our entry to Google Science Fair, we would greatly appreciate any "likes," "shares," "pins," or anything else you can think of! Please give our YouTube video a "thumbs up" and take the time to also vote for us here on Instructables! Thank you!


supercapacitor (author)2014-07-04

This is awesome!

TrollFaceTheMan (author)2014-07-04

Very cool concept!

thassaj (author)2014-05-18

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.

astral_mage (author)thassaj2014-05-28

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

deamon4 (author)thassaj2014-05-19

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 :)

rusty1300 (author)2014-05-16

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

CEVMarauder (author)2014-05-15

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

JahnaviJ3 (author)2017-06-14

I'm new to this topic and was intrested to contruct MFC.Can you please explain this sentence in your article "The PEM was stretched over one end of the PVC segment and then both segments were attached to each other using the coupler, thus locking the PEM in place."

dproteus (author)2014-05-15

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 :)

TavoR3 (author)dproteus2016-05-23

4 homemade microbial fuel cells, connected in series, can light a white LED.

xKOBAYASHIMARUx (author)dproteus2014-05-16

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

dproteus (author)xKOBAYASHIMARUx2014-05-16

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. which was the first or second result from Google at the time. Like I said, just a quick search. ..

xKOBAYASHIMARUx (author)dproteus2014-05-16

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! :)

SHOE0007 (author)2015-12-16

I heard you can make a electrode out of pipe and agar. I saw a instructable on making a silver electrode with KCl and agar. I am going to modify this by adding 0.001% Malachite green sol to agar. Two strippling made of copper and stainless steel since It would be harder to extract a big enough carbon electrode without any mess. The Malachite green prevents abnormal growth of bacteria. The broth will be boiled and milk powder and bacteria will be added. The pipes PVC will have Potassium chloride saturated solution to enhance electron production. A air pump will provide air. Potassium ferrocyanide 0.05 to 0.5 moles will be added. Hopefully this will work!!

SHOE0007 (author)2015-12-09

Your idea to make a probe gave me an Idea. How about you use a old or new ph probes and connect the wires properly and see if you get any better voltage and current. It may do this. You need pretty small pcb pipes and water proof sealant.

A mesh from fine cheese cloth that blocks the debris or teflon filters perhaps if they exist.


SHOE0007 (author)2015-12-09

I made a weak closed system version of this. It peaks the following volts and current.

730 mV

4.7 mA


0.730 V* 0.0047 A = 0.0034 W = 3.43 mW power.

Not much but without oxygen pump the power was in microamps. 6 uA.

572 times more powerful than my last one.

ian.gallinger (author)2015-04-23

lol i live right next to mlhs

even beat them in football

mahajengannisa (author)2015-04-03

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

ccpro14 (author)2015-01-21

cool one man but i dont understand the building concept

anjaneyulu123 (author)2014-08-24

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

jferkans (author)2014-07-14

Holy genius... I wish I had a brain like that and the ingenuity you do

luillo125 (author)2014-06-10

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

shomas (author)2014-06-02

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.

manuka (author)2014-05-17

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 ".

robosilo (author)2014-05-17

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

bkonfuzius (author)2014-05-17

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).

manuka (author)2014-05-15

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 =>


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 (author)manuka2014-05-15

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

wilgubeast (author)kasisnu2014-05-16

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

kasisnu (author)wilgubeast2014-05-17

Thank you! :)

moebuspcgold (author)wilgubeast2014-05-16

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

moebuspcgold (author)manuka2014-05-15

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

ASCAS (author)2014-05-16

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

ianmcmill (author)2014-05-16

This is nice !

Mikel99 (author)2014-05-16

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

arthur verburg (author)2014-05-16

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?

hqmhqm (author)2014-05-16

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.

triiiiiple (author)2014-05-16

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.

rspellicer (author)2014-05-16

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

rich_moe (author)2014-05-15


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.

tygger281 (author)2014-05-15

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?

ElectroFrank (author)tygger2812014-05-15

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

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

ar_caver (author)2014-05-15

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

Ninjabdou (author)2014-05-15

Great; this is amazing

neowton (author)2014-05-15

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.

JoshHawley (author)2014-05-15

An interesting idea, but, without current measurements and more testing, the data is not particularly useful. You need to have a control test with clean water, and another one with just pond water. Without the control tests, you do not know how much of it (if any) was generated by the microbes.

alcurb (author)2014-05-15

Cool project, but you are missing the construction steps and some essential details.

What are the details of how to build the PEM chamber?

You said "PEM's may be acquired naturally through chicken eggs": How do you acquire the membrane from the egg? How do you prepare the egg membrane to be used as a PEM? Obtaining Nafion 117 might be out of the question for developing nations.

Also, developing countries need to have access to chemicals to keep the Ph at 7.7. What specifically would that chemical be for the developing country to obtain? How would they know that they have reached the optimum Ph? Litmus paper? How easy would it be for a poor village to get their hands on Litmus paper or other type of Ph meter?

Don't get me wrong; I applaud your experiment, but you need to put out more data and step-by-step construction details so that others can reproduce your experiment to validate it.

Good work overall.

runical (author)2014-05-15

Seems nice, but do you have any data on the actual power produced? As you know, P = V*I, so without the current, there is no useful data. It's like measuring the voltage of a battery and saying that, yes, it can supply a current.

So, if you really want to confirm (or invalidate) your hypothesis, you will need to actually provide a load for the system and measure the power produced.

ac-dc (author)2014-05-15

The energy needed to transport the water, setup and maintain such a generator is likely to significantly exceed the electrical output plus storage losses. Thus, it may be valid as a science experiment to show that waste water can produce electricity, but it is premature and short sighted to pretend this is a solution to electricity production problems anywhere.

Not so ironically this is why information already available to high school students isn't being widely used for this purpose. Science is great to learn but the devil is in the details.

w1bmw (author)ac-dc2014-05-15

I concur. Lack of water is a bigger problem for mankind than lack of electricity any day. I love this kind of science and it has to be done, but the costs have to be examined and they are often greater than the rewards.

About This Instructable




Bio: "Things don’t have to change the world to be important." Twitter: @PancakePatrol, Google+: Austin Simonson
More by austinsimonson:Ninja Turtle CupcakesHyduino - Automated Hydroponics with an ArduinoSand "Clay" - Preserve Your Sand Creations Forever!
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