Home Project Ideas Project Guide Ask An Expert Blog Careers Teachers Parents Students

How Do Bacteria Produce Power in a Microbial Fuel Cell? *

Difficulty
Time Required Very Long (1+ months)
Prerequisites Previous experience using a voltmeter/multimeter is helpful, but not required. A basic knowledge of how to work with bacteria is also needed to complete this science fair project. Consult the Microbiology Techniques and Troubleshooting guide for information on how to conduct microbiology experiments.
Material Availability The microbial fuel cell needs to be special ordered from the Science Buddies Store. Other specialty items, like the media to grow bacteria on, can be ordered from online vendors such as Carolina Biological Supply Company.
Cost Average ($50 - $100)
Safety Be sure to wear the gloves supplied with the kit when handling the microbial fuel cell’s electrodes (its cathode and anode). The electrodes are made of a conductive material called graphite fiber and should not be placed near electronics or power plugs, or have their fibers dispersed in the air. Use sterile technique when growing the bacteria. Read the Microorganisms Safety Guide before starting any experiments. SRC approval may be necessary. Adult supervision is recommended.
*Note: This is an abbreviated Project Idea, without notes to start your background research, a specific list of materials, or a procedure for how to do the experiment. You can identify abbreviated Project Ideas by the asterisk at the end of the title. If you want a Project Idea with full instructions, please pick one without an asterisk.

Abstract

Topsoil is packed with bacteria that generate electricity when placed in a microbial fuel cell (MFC). Because such bacteria-laden soil is found almost everywhere on Earth, microbial fuel cells can make clean, renewable electricity nearly anyplace around the globe. As natural resources are being depleted, scientists' attention has shifted to pursuing alternative energy sources, such as MFCs, even more than before.

A microbial fuel cell, also known as a biological fuel cell, is a device that can use microbes to generate electricity. An MFC has two electrodes and an area that separates the electrodes (called a membrane). For an MFC to function, electricity must flow into one electrode and leave the other electrode. How is this accomplished? It has to do with the bacteria in the MFC. Some types of soil bacteria can help generate electricity. These bacteria, known as electrogenic bacteria, include the Shewanella species, which can be found in almost any soil on Earth and are shown in Figure 1, below, and the Geobacter species, which prefer living in soil deep underground or even under the ocean, where no oxygen is present. The soil bacteria eat what is in the soil, such as microscopic nutrients and sugars, and in turn, produce electrons that are released back into the soil. Electrons are subatomic particles that have a negative charge. These electrons can be harnessed and used to create electricity, which is a form of energy.


Figure 1. This is a high-magnification image of Shewanella bacteria, specifically the species S. oneidensis. The bacteria are the cylindrical-shaped rods scattered in this image. (The other parts of the image are ice pieces that the bacteria were submerged in to take this picture.) (Image credit: PLoS Biology)

In an MFC using these soil bacteria, one electrode (specifically the anode) is buried down in damp soil. Down there, the bacteria multiply and cover the electrode (creating a biofilm on it), supplying it with a lot of electrons. At the same time, the other electrode (called the cathode) is placed on the top of the soil, leaving one of its sides completely exposed to the air. Electrons from the bottom electrode travel up a wire to the top electrode and, once there, they react with oxygen (from the air) and hydrogen (made by the bacteria as it digests nutrients in the soil) to create water.

What do you think happens to the quantity of bacteria in the MFC as the power output increases? Does the number of bacteria, increase, decrease, or stay relatively stable? One way to investigate this would be to take a swab of the soil at the beginning of the experiment and grow the bacteria from the swab, and then take a swab when the power output is much greater and grow the bacteria from that swab. Do you see more bacteria growing on the nutrient agar plate from the second swab taken? Do you see different types of microbes growing? To learn how to set up the microbial fuel cell and take power output measurements, see Science Buddies' science project ideas Turn Mud into Energy with a Microbial Fuel Cell — and a Dash of Salt and Powered by Pee: Using Urine in a Microbial Fuel Cell. For an idea of how to take bacterial swabs and grow them on agar plates, see Science Buddies' science project idea Is That Really Bacteria Living in My Yogurt? (Note: Shewanella bacteria can be aerobic [they need oxygen] or anaerobic [they grow without oxygen], and Geobacter bacteria are anaerobic. Knowing this, why do you think an anaerobic chamber might be ideal for doing this experiment?).

Credits

Teisha Rowland, PhD, Science Buddies

Cite This Page

MLA Style

Science Buddies Staff. "How Do Bacteria Produce Power in a Microbial Fuel Cell?" Science Buddies. Science Buddies, 30 June 2014. Web. 26 July 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_p032.shtml>

APA Style

Science Buddies Staff. (2014, June 30). How Do Bacteria Produce Power in a Microbial Fuel Cell?. Retrieved July 26, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_p032.shtml

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.


Last edit date: 2014-06-30

Bibliography

These resources will give you more information about microbial fuel cells and the bacteria involved:

Materials and Equipment Product Kit Available

This is an abbreviated project idea, which means you will have to write your own Experimental Procedure and use it to create your own Materials list. In general, think about the fact that you will need a microbial fuel cell, mud, petri dishes with agar for growing your bacteria, and other bacteria growing supplies. The other Project Ideas linked to in the Background tab can help you figure out your Procedure and Materials list.

Order Product Supplies

Buy Kit
Project Kit: $59.95

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Ask an Expert

Contact Us

If you have purchased a kit for this project from Science Buddies, we are pleased to answer your questions.

In your email, please follow these instructions:
  1. What is your Science Buddies kit order number?
  2. Please describe how you need help as thoroughly as possible:

    Examples

    Good Question I'm trying to do Experimental Procedure step #5, "Scrape the insulation from the wire. . ." How do I know when I've scraped enough?
    Good Question I'm at Experimental Procedure step #7, "Move the magnet back and forth . . ." and the LED is not lighting up.
    Bad Question I don't understand the instructions. Help!
    Good Question I am purchasing my materials. Can I substitute a 1N34 diode for the 1N25 diode called for in the material list?
    Bad Question Can I use a different part?

Contact Us

Related Links

If you like this project, you might enjoy exploring these related careers:

female microbiologist looking in microscope

Microbiologist

Microorganisms (bacteria, viruses, algae, and fungi) are the most common life-forms on Earth. They help us digest nutrients; make foods like yogurt, bread, and olives; and create antibiotics. Some microbes also cause diseases. Microbiologists study the growth, structure, development, and general characteristics of microorganisms to promote health, industry, and a basic understanding of cellular functions. Read more
Environmental Scientist evaluating toxin effects on frogs

Environmental Scientist

Have you ever noticed that for people with asthma it can sometimes be especially hard to breathe in the middle of a busy city? One reason for this is the exhaust from vehicles. Cars, buses, and motorcycles add pollution to our air, which affects our health. But can pollution impact more than our health? Cutting down trees, or deforestation, can contribute to erosion, which carries off valuable topsoil. But can erosion alter more than the condition of the soil? How does an oil spill harm fish and aquatic plants? How does a population of animals interact with its environment? These are questions that environmental scientists study and try to find answers to. They conduct research or perform investigations to identify and eliminate the sources of pollution or hazards that damage either the environment or human and animal health. Environmental scientists are the stewards of our environment and are committed to keeping it safe for future generations. Read more
fuel cell engineer with fuel cell model

Fuel Cell Engineer

Most of the world's energy comes from fossil fuels. However, the amount of fossil fuels is finite, and many people are concerned about where our energy will come from in the future. We can turn to alternative, renewable sources of fuel, such as our sun (solar energy) and the winds (wind energy). But what happens when the sun doesn't shine or the winds don't blow? Would we be stuck? Well, that is where the fuel cell comes in. A fuel cell is an electrochemical device that generates electricity through a reaction between a fuel, like hydrogen, and an oxidant, like oxygen. This reaction produces few greenhouse gas emissions other than water or water vapor. The job of the fuel cell engineer is to design new fuel cell technology that improves the reliability, functionality, and efficiency of the fuel cell. Do you like the idea of using your math and science skills to work on mankind's future energy needs? Then start "fueling your future" and read more about this career. Read more
electrical engineer aligning laser

Electrical & Electronics Engineer

Just as a potter forms clay, or a steel worker molds molten steel, electrical and electronics engineers gather and shape electricity and use it to make products that transmit power or transmit information. Electrical and electronics engineers may specialize in one of the millions of products that make or use electricity, like cell phones, electric motors, microwaves, medical instruments, airline navigation system, or handheld games. Read more

Looking for more science fun?

Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.

Find an Activity