On the other hand, if you found that the peak power could be produced using resistors greater than the ones supplied in the Science Buddies MFC kit, you can use larger resistors to test this. For additional ideas focusing on the biological aspects of the microbial fuel cell, see the Science Buddies science projects, If the hacker board is not set up correctly, the LED will not blink. Make sure you wrap the wire snugly around the straw. PMC If you need help using a multimeter, consult the Science Buddies reference. Science Buddies participates in affiliate programs with The peak power is the highest power produced by any of the resistors. The Microbial Fuel Cell Kit needs to be special-ordered from our partner, Be sure to wear the gloves supplied with the kit when handling the microbial fuel cell's electrodes (its cathode and anode). How does this happen? 2017 Jul 15;356:225-244. doi: 10.1016/j.jpowsour.2017.03.109. Will it increase, decrease, or stay relatively stable? When you are done, you should have about 400g of fine, sifted soil in the bowl. Most researchers have been working on determining how bacteria transfers electrons and what kind of bacteria produces more current to design more efficient methods to transfer electrons. As 1gram (g) of soil contains up to trillions of individual bacteria, you will have to make a serial dilution of your sample before you can plate it on the agar plates. Repeat steps 6 and 7 using the cathode (the thicker, black, felt-like circle) and the orange wire (which is shorter than the green wire). If you are having trouble with this project, please read the FAQ below. The open circuit voltages of individual microbial fuel cells were 0.689, 0.682, and 0.686 V, respectively. Then assemble the MFC exactly as you put it together before, following the instructions from the "Setting Up the Microbial Fuel Cells and Bacteria Count" section to make sure that the wires are twisted together properly and everything is reconnected to the hacker board correctly. One easy way to figure out how to troubleshoot your experiment is reviewing the flow chart in Figure 10. Next, measure the power output for both of the MFCs using the same multimeter as for your conductivity measurement circuit. These resources will give you more information about microbial fuel cells, electricity, soil conductivity: For more information about electronics terms and using a voltmeter/multimeter, use these primers: These specialty items can be purchased in a kit from our partner (In the salt electrolyte, there is a positively charged sodium ion and a negatively charged chlorine ion). Our team of volunteer scientists can help. Set your multimeter to measure direct current in the 2000A range on the upper-right part of your multimeter dial. (The anode is the thinner, black, felt-like circle.). The MFCs should remain in the same location the entire time after you set them up because if they are moved, this could disrupt the growth of the bacteria. Wrap the second piece of wire around the other end of the straw tube a few times, leaving a 5cm (2inch) tail of wire. Assemble the conductivity sensor, as shown in Figure 6. Gajda I, Stinchcombe A, Merino-Jimenez I, Pasternak G, Sanchez-Herranz D, Greenman J, Ieropoulos IA. Microbial fuel cells (MFCs), as sustainable bioelectrochemical systems, can simultaneously realize sewage treatment and power generation by utilizing electroactive bacteria (EAB) (Liu et al., 2021).MFCs have attracted extensive attention in wastewater biological treatment owing to their low operating cost, no biofouling, and wide range of substrates. Why? The https:// ensures that you are connecting to the Bookshelf J Power Sources. If the temperature of the room that the microbial fuel cell is in is very cold, the bacteria may not grow well, which would decrease the peak power output. If the voltage seems to be changing a littlesuch as decreasing slightly over the period of a few secondswatch the readings on the multimeter for a few seconds more until they stabilize (and stay the same for a few seconds). Gently place the cathode on top of the mud and press it as flat as you can, as shown in Figure 5. With substrate metabolism and EET, protons are also released into the anode . A review. This way you can make sure that you only get a small number of colonies on each plate, making them easier to count. Keep in mind that the soil conductivity is not the only factor that affects the power output of an MFC. Would the MFC continue to produce more and more power, or would it crash after a while because, perhaps, the bacteria will have died from the excess of salt? If you like this project, you might enjoy exploring these related careers: You can find this page online at: https://www.sciencebuddies.org/science-fair-projects/project-ideas/MicroBio_p032/microbiology/bacteria-microbial-fuel-cell. Record your results for both of the microbial fuel cells in your lab notebook in a data table like Table 3. FAQ: How Do Bacteria Produce Power in a Microbial Fuel Cell? Soil from just about anywhere works from a backyard, park, open space, or even a riverbed. Again, mix until the salt is completely dissolved. Take a sample of your prepared soil for measurement of the initial bacteria quantity. After the resistor has been plugged in for 5 minutes, use your multimeter to measure the voltage across the resistor. Identify the different components and use masking tape and a permanent marker to label one of the devices with "1g salt" and the other one with "5g salt". Thanks to Bob Rowland, ColdQuanta Inc., for assistance with testing this project, and to Ben Finio, PhD, and Howard Eglowstein, Science Buddies, as well as Keegan Cooke, Executive Director at Keego Technologies LLC, for their feedback. A sample graph is shown in Figure 9. Investigate other parameters, such as temperature or soil conductivity and soil moisture. What do you think would happen if you added even more salt? (The anode is buried deep enough, where there is no oxygen, so this reaction could not take place right next to the anode.) Also make sure that none of the exposed parts of the wires are touching each other. What was the peak power at this time? It is possible that the LED has become damaged. Clipboard, Search History, and several other advanced features are temporarily unavailable. Take a clean spoon and use it to dig into the top 12cm of the soil. After about 714 days, the power output should stabilize. Now you can start doing your initial bacteria count using the plate count method. Use Figure 8 to determine the resistance for each resistor. Which soil is best, resulting in the MFC generating the most power? If the temperature of the room that the microbial fuel cell is in is very cold, the bacteria may not grow well, which would decrease the peak power output and affect whether the LED blinks. What do you think will happen to the power output once you increase the soil conductivity of your MFC? Santoro C, Winfield J, Theodosiou P, Ieropoulos I. Bioresour Technol Rep. 2019 Sep;7:100297. doi: 10.1016/j.biteb.2019.100297. Even if the hacker board is set up correctly, some of the wires might be loose or may not be making good electrical contacts in the hacker board. Write to us at For example, if we add something to the soil, would it make the MFC produce electricity better, increasing the amount of power it makes? How do soil bacteria help make electricity in an MFC? When printing this document, you may NOT modify it in any way. Electrons from the anode travel up a wire to the cathode and, once there, they react with oxygen (from the air) and hydrogen (produced by the bacteria as it digests the nutrients in the soil) to create water. The orange wire from the cathode should be sticking out of the top side. Table 1 summarizes the electrical variables, their units, and abbreviations. Also, if the microbial fuel cell is moved to a different location (particularly if it is at a different temperature), this could disrupt the growth of the bacteria. If the power output does not seem to be stabilizing after the addition of salt, try waiting a little longer. Fig. Make sure that you are, If there are air bubbles trapped in the damp topsoil in the microbial fuel cell, this can prevent the bacteria from growing well because they do not want to be exposed to oxygen. Soil is packed with bacteria that generate electricity when placed in a microbial fuel cell (MFC). Then remove the orange wire from the "+" port and plug it into port 3. As a biofilm made of the electrogenic bacteria Shewanella and/or Geobacter forms on the buried anode they produce electrons which are transferred from the anode to the cathode through the wires. It is important to remove these particles from the soil because they can. The anode and the cathode electrodes and proton exchange membranes (PEM) are important components affecting the performance and operation of MFC. Power output limitation is one of the main challenges that needs to be addressed for full-scale applications of the Microbial Fuel Cell (MFC) technology. The green wire from the anode should be sticking up. The more electron-producing, soil-munching bacteria are in the soil, the more electricity the MFC produces. Use Figure 8 to determine the resistance for each resistor. Experiments performed with several lipopolysaccharide (LPS) mutants (waaC, waaF and waaG) of E. coli BW25113 that increase the outer membrane permeability found the power generated by two of the truncated LPS mutants, i.e., waaC and waaF, to be significantly higher (5.6 and 6.9 mW/m2, respectively) than that of the wild-type E. coli BW25113 (2.6 mW/m2). the url. In another mini cup add 5g of table salt to 5mL distilled water. If your soil is dry, carefully open the microbial fuel cell and mix distilled water into the soil until it is moist again. The Plant-Microbial Fuel Cell (P-MFC) is a technology that could produce sustainable bio-electricity and help meeting the increasing energy demand. Power output gradually decreases in the two following data points to about 43.5 and 33 microwatts at 2200 and 4700 ohms respectively. The .gov means its official. However, even if the LEDs never blink, you may still be able to do this science project; be sure to continue to take the power output measurements every day. Energy Environ Sci. If you use several different resistors, you can generate a power-resistance curve, which allows you to determine the maximum power output of your microbial fuel cell, as explained in more detail in the Procedure. Make a note in your lab notebook of what the peak power for both MFCs is each day, by circling or highlighting this value in your data table. They are also used to power fuel cell vehicles, including forklifts, automobiles, buses, trains, boats, motorcycles and submarines. Before Which bacteria are used in microbial fuel cells? Label a mini cup with the date and time, and use your sterilized spoon to scoop about 23 spoons full of your prepared soil (you will need 0.5g) into the cup. Close the lid and set it aside for now. When enough electrons are created by the bacteria the lightbulb will be lit. Accessibility Make two graphs of your data for each microbial fuel cell, one showing how the power output changed over time and one showing how the frequency of LED blinks changed over time. This is a high-sensitivity setting that you will. Then use a clean transfer pipette to suck up some salt solution from the cup with 1g salt and spread it on top of the mud, mix it in, and then dig around inside of the mud, adding all of the salt solution and mixing it in as you go. Repeat this experiment, but this time, vary the electrode spacing in both MFCs. Microbial Fuel Cell scheme (A) and the photograph of single MFC unit (B). Set the multimeter to measure DC voltage. Front Energy Res. An example is shown in Figure 7. Santoro C., Arbizzani C., Erable B., Ieropoulos I. Microbial fuel cells: from fundamentals to applications. For step 2, you should see the power output slowly increase. You can calculate this by using a derivation of Ohm's law, as described in the. The sugar should change the power output of the MFC. Finally, prepare your soil sample and measure its conductivity. If you like this project, you might enjoy exploring these related careers: You can find this page online at: https://www.sciencebuddies.org/science-fair-projects/project-ideas/Elec_p071/electricity-electronics/energy-microbial-fuel-cell-conductivity. The MFCs (mean values of triplicated data) were fed with activated sludge wastewater supplemented with sodium acetate as the carbon energy source. Write to us at, Microbiology Techniques and Troubleshooting. Scoop about 1 teaspoon of soil into a fresh mini cup, labeled with time, date, and microbial fuel cell type (sugar treatment or control) for the bacteria plate count. Was there an increase or decrease in power output? Microbial fuel cells (MFCs) are however very sensitive to changes in the configuration, source of inoculums and substrate initial pH values. Place a plastic strainer or colander over a large mixing bowl. Prepare three mini cups for the serial dilution and label them 10. Use the bacteria plate count method again to measure the numbers of bacteria in both microbial fuel cell soil samples, following. Science Fair Project Display Boards, report, or however you are presenting your project) your question, your hypothesis, what you anticipated would happen, then what you actually saw (such as your peak power output measurements over time), your questions about what was happening, and your attempts to troubleshoot. The arrow indicates the cathode replacement from catalyst based to non-catalyst based material (inset). eCollection 2021 Aug 20. The dotted line represents a linear regression fit that shows the direct relationship between these two parameters. Use the stabilized value. Then clip the multimeter's black lead to the resistor's metal wire that is plugged into port 6, as shown in the video. What do you think are good devices that could be powered by a microbial fuel cell? Evaluation of artificial neural network algorithms for predicting the effect of the urine flow rate on the power performance of microbial fuel cells. You will find more detailed information in the FAQ section below. Go through some of your data and create a graph showing power output (in W) on the x-axis and blinks per second on the y-axis. If one or both of the LEDs are blinking, time how many seconds apart the blinks for each one are. Wherever it stabilizes, it should make enough power to for the LED to blink at least once every 30 seconds. When enough electrons are created by the bacteria the lightbulb will be lit. The resistor you use to find the peak power tells you what the. You will need a peak power output of. When you think of electricity, and how it can be made naturally, you may think of lightning and electric eels; you probably do not think about microbes! Now set your multimeter to measure direct current in the 20mA range on the right side of the multimeter dial. For the resistors, the orientation does not matter. HHS Vulnerability Disclosure, Help What do you think will happen if you put the electrodes closer together? You may find the answer to your question. Santoro C, Garcia MJS, Walter XA, You J, Theodosiou P, Gajda I, Obata O, Winfield J, Greenman J, Ieropoulos I. ChemElectroChem. How much more voltage and current would you need to power other devices? Supercapacitive paper based microbial fuel cell: High current/power production within a low cost design. Please enter a search term in the text box. Investigate how changing the soil conductivity inside a microbial fuel cell affects its power output. Put on the gloves that came with the MFCs and start assembling the first microbial fuel cell. Brush-like polyaniline nanoarray modified anode for improvement of power output in microbial fuel cell . Before you proceed, convert all of your current measurements to amps (A). Previous experience using a multimeter and familiarity with the physics of electricity is helpful, but not required. 2020 Dec 15;748:141425. doi: 10.1016/j.scitotenv.2020.141425. Use a clean paper towel or rag to wipe any mud off the vessel's rim. Wherever it stabilizes, it should make enough power to blink the LED at least once every 30 seconds. Remove the MFC anode from its bag (the anode is the thinner, black, felt-like circle). A flow chart seperates a microbial fuel cell experiment into 3 time ranges and provides a diagnosis for 3 problems that may occur during the experiment. Rinse the mud off your gloves and dry them. The microbial fuel cell should be kept indoors, at normal room temperatures (about 1925C, or 6677F), in the same location the entire time after you set it up. Time a 10-second interval and count how many times the LED blinks in this period and then divide this by 10 to get blinks per second. B) Shows the average efficiency range of these fuel sources. Can you change the power output by feeding the bacteria inorganic and organic substrates in the form of waste products? Most bacteria will need at least 24-48 hours at room temperature to form visible colonies. Our top priority is student learning. Microbial Fuel Cell Kit available from our partner, Digital clock/thermometer to be powered by the microbial fuel cell (1), Bacteria Discovery Kit, available from our partner, Optional: Old newspapers to protect your work area, Soil (at least 4 cups) or about 400g of sifted soil. You can make a bar graph for both MFCs showing the soil conductivity before and after adding salt on the x-axis and the corresponding maximum power output on the y-axis. When was the power output and blinking frequency the highest for each of the MFCs? You can either watch the video below or follow the step-by-step instructions. Why do you think this is the case? Although it will not be explored in this science project, you might like to know that the peak power tells you what the. Get the right supplies selected and tested to work with this project. Put the lid on the mini cup and set it aside for now. To do this, start a stopwatch as soon as you see the LED blink and stop the stopwatch when the LED blinks again. Can you think of other means to change the internal resistance of a microbial fuel cell besides increasing or decreasing the soil conductivity? So, for an MFC to function, electricity must be made to flow into the anode and then leave from the cathode. Twist the other wire tail of the conductivity sensor around the metal end of the black lead from the. Do not let any mud or liquid cover the top of the cathode. The time between LED blinks should also stabilize. until you have tested the MFC with all of the resistors in the kit. At the same time, the other electrode (called the cathode) is placed on top of the soil, leaving one of its sides completely exposed to the air. xylitol sinus rinse. To measure the MFC's power output, remove the capacitor and LED from the hacker board. Read the. When it stabilizes, the peak power should not change by more than about 10% for at least three days in a row. Calculating the conductance is easyit is the current divided by the voltage, as shown in Equation 2.
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