Introduction: 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
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.
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!
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