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Bacteria can be used to generate electricity

Bacteria can be used to generate electricity (Let’s Talk Science using image by Gerd Altmann and raphaelsilva via Pixabay)

STEM in Context

Microbial Fuel Cells

Magdalena Pop

Summary

In a few decades, some of the electricity you use might be generated by bacteria.

Yesterday, my TV remote stopped working. Its batteries had died. I feel bad every time this happens. Used batteries make toxic junk. Also, a dead remote reminds me how much my lifestyle depends on electricity! 

Many common energy sources and technologies are fraught with problems. We use a lot of non-renewable fuels to generate electricity. For example, we use coal, oil and natural gases to generate electricity. But these will eventually run out. In the meantime, they mess up the environment. They cause air pollution and climate change.

We need smarter alternatives. We need renewable energy sources. And we need technologies that are friendlier to the environment. One of these smart alternatives could come from the oldest, smallest, and most adaptable creatures on the planet: bacteria.

Like all living cells, bacteria need energy. Some bacteria produce their own energy. They do this through a process called anaerobic cellular respiration. Anaerobic means “without air.” These bacteria typically live in a low-oxygen environment. You may be familiar with the process of photosynthesis. During photosynthesis, plants turn carbon dioxide and water into the sugars they use for energy. Cellular respiration is essentially this process in reverse. It breaks down sugars into water, carbon dioxide and (most importantly) adenosine triphosphate (ATP). ATP is the energy molecule that all cells need to function. 

The chemical formula for cellular respiration is:

The chemical formula for cellular respiration
Chemical formula for cellular respiration ©2019 Let’s Talk Science).

 

Text version

C6H1206 plus 6O2 becomes 6CO2 plus 6H2O plus approximately 39 ATP.

 

Scientists have found a way to capture the energy that cellular respiration creates. They do this with a technology called a microbial fuel cell (MFC)

Did you know?

The English botanist M.C. Potter was the first person to generate electricity from bacteria. He generated electricity from E. coli back in 1911! 

How do batteries generate electricity? 

How do MFCs work? First, let’s look at how an ordinary dry cell battery works. A battery generates electricity using chemical energy. In a battery, one of the electrodes (the anode) undergoes an oxidation reaction. This is a chemical process that gives off electrons. The electrons travel through a paste of manganese oxide to the other electrode (the cathode). Here, the electrons undergo a reduction reaction. This is a chemical process in which electrons are absorbed. As the electrons move from anode to cathode, they create an electric current. This can do work, such as power a light bulb.

Parts of a dry cell battery including the direction of flow of electrons
Parts of a dry cell battery including the direction of flow of electrons (Let’s Talk Science using an image by Graphic_BKK1979 via iStockphoto).

How are MFCs different from ordinary batteries? 

Just like an ordinary battery, an MFC uses chemical energy to generate electricity. An MFC has two electrodes held in separate chambers. The anode chamber that contains the bacteria is anaerobic. This means that it does not contain oxygen. The cathode chamber is aerobic. That means it does contain oxygen. The oxidation process occurs inside the bacteria living in the anode chamber. This takes advantage of the oxidation that bacteria carry out naturally during cellular respiration. Electron bonds hold together the molecules in the food that bacteria eat. The bacteria break those bonds to release the electrons.

Electricity from plants by Plant-e BV (1:51 min.).

Cellular respiration can continue for as long as the bacteria have food. Bacteria can digest pretty much anything. They can digest human waste. They can also digest other waste products such as ammonia, ethanol, or acetate. This makes MFC technology really attractive. It can generate electricity and get rid of waste at the same time! 

Generating electricity using bacteria is not a new idea. In fact, it’s been around for over a century. So why hasn’t MFC technology delivered on its promise yet? The design and materials used to build the electrodes have greatly improved. But MFCs still generate relatively low currents. Why? One reason is that electrons given off during cellular respiration don’t transfer well from the bacteria to the anode.

Bacteria used in MFCs are called exoelectrogens. They are electrochemically active and can transfer electrons outside their cells. The electrons they give off reach the anode in one of three ways.

  1. They can be transported by protein carriers on the cell surface.
  2. They can be exported through cell membrane projections (nanowires).
  3. They can be secreted in chemical solutions (mediators).
Electrons can be carried by protein carriers (A), nanowires (B) or mediators (C)
Electrons can be carried by protein carriers (A), nanowires (B) or mediators (C) (© 2019 Let’s Talk Science).

Did you know?

Microbial electrolysis cells (MECs) are a type of modified microbial fuel cell. MECs use outside power to produce fuel, such as hydrogen.

What is the future of MFCs? 

One day, MFC technology could be used to generate power with biodegradable waste and sewage. At the same time, it could provide help with wastewater treatment and bioremediation. MFCs could also help monitor the amount of biodegradable material left in wastewater streams. They could also help with remote sensing. These tasks could be done by self-powered devices using MFCs. 

Electrifying Wastewater: Using Microbial Fuel Cells to Generate Electricity (2013) by the Bruce Logan of The American Chemical Society (2:11 min.).

Did you know?

Researchers are also exploring whether MFC technology could power equipment in space. 

Could these natural mechanisms be enhanced? Scientists are trying to answer this question using genetic engineering. They manipulate the genes involved in the electron transfer. They also manipulate other genes key to the life cycle of bacteria. This line of research is still young but holds a lot of promise.

So will MFCs power my TV remote in the future? Probably not. Unlike ordinary batteries, MFCs require a constant inflow and outflow of materials. In particular, they need a steady supply of food for bacteria at the anode. This is clearly not an option in a TV remote.

Summing up

Will bacteria one day generate some electricity you use? It is very possible. This electricity generation process might help deal with waste. It may even help clean up contaminated soil and water. This is just one among several new alternative energy sources. Energy generation in the future might be much cleaner and more sustainable than today. 

Starting Points

Connecting and Relating
  • How many devices do you have that require battery power to work? What kind of batteries do you use in these devices? What happens to the spent batteries that you use? 
  • Do you use any forms of renewable energy in your daily life? Which types of renewable energy? What object(s) does this energy operate? 
  • Would you like to see MFC technology used in your community? Why or why not? 
Connecting and Relating
  • How many devices do you have that require battery power to work? What kind of batteries do you use in these devices? What happens to the spent batteries that you use? 
  • Do you use any forms of renewable energy in your daily life? Which types of renewable energy? What object(s) does this energy operate? 
  • Would you like to see MFC technology used in your community? Why or why not? 
Relating Science and Technology to Society and the Environment
  • Technologies like the MFC are often developed to fix problems created by our lifestyle. It would be better to change our lifestyle instead: use less electricity and produce less waste. Do you agree? Why or why not?
  • If MFCs used genetically-engineered bacteria, what would be the risks? Can these risks be prevented? Explain.
  • Is the development of efficient MFC technology something that we should use public tax dollars to develop? Why or why not?
Relating Science and Technology to Society and the Environment
  • Technologies like the MFC are often developed to fix problems created by our lifestyle. It would be better to change our lifestyle instead: use less electricity and produce less waste. Do you agree? Why or why not?
  • If MFCs used genetically-engineered bacteria, what would be the risks? Can these risks be prevented? Explain.
  • Is the development of efficient MFC technology something that we should use public tax dollars to develop? Why or why not?
Exploring Concepts
  • What is renewable energy? What characteristics should renewable energy sources have? Explain and give examples.
  • What are oxidation-reduction reactions and how are they useful in electricity?
  • How does an electrochemical cell work?
  • What happens during cellular respiration, and how is this process put to use in a microbial fuel cell?
Exploring Concepts
  • What is renewable energy? What characteristics should renewable energy sources have? Explain and give examples.
  • What are oxidation-reduction reactions and how are they useful in electricity?
  • How does an electrochemical cell work?
  • What happens during cellular respiration, and how is this process put to use in a microbial fuel cell?
Nature of Science/Nature of Technology
  • How is the development of MFC technology an interdisciplinary effort? Which disciplines are involved, and what aspect of the technology does each of them focus on?
  • Technology finds inspiration in natural processes. How does this idea apply to the MFC?
  • Since we have not been able to perfect the MFC technology in over a century, should we give up? Why or why not?
Nature of Science/Nature of Technology
  • How is the development of MFC technology an interdisciplinary effort? Which disciplines are involved, and what aspect of the technology does each of them focus on?
  • Technology finds inspiration in natural processes. How does this idea apply to the MFC?
  • Since we have not been able to perfect the MFC technology in over a century, should we give up? Why or why not?
Media Literacy
  • Politicians often talk about “an energy crisis.” Is the urgency implied in this phrase justified? Explain.
  • When people hear of alternative energy, they usually picture solar panels and wind turbines. How could popular media be used to help people visualize microbial fuel cells?
Media Literacy
  • Politicians often talk about “an energy crisis.” Is the urgency implied in this phrase justified? Explain.
  • When people hear of alternative energy, they usually picture solar panels and wind turbines. How could popular media be used to help people visualize microbial fuel cells?
Teaching Suggestions
  • This article and embedded videos can be used for Chemistry, Biology, Engineering & Technology,  and Earth & Environment teaching and learning related to electrochemistry, electricity generation, redox reactions and renewable energy. Concepts introduced include renewable energy sources, bacteria, cellular respiration, microbial fuel cell (MFC), battery, electrodes, anode, cathode, oxidation reaction, reduction reaction, electric current, exoelectrogens, protein carriers, mediators, genetic engineering and wastewater management.
  • After reading the article and viewing the embedded videos, teachers could have students do a Key Ideas Round Robin learning strategy to consolidation new information. Ready-to-use Key Ideas Round Robin reproducibles are available in [Google doc] and [.pdf] formats. 
  • To consolidate understanding of microbial fuel cells (MFC), teachers could have students complete a Concept Definition Web learning strategy. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [.pdf] formats. 
  • To consider the positive and negative issues related to microbial fuel cells, students could do a Pros & Cons Organizer learning strategy. Ready-to-use Pros & Cons Organizer reproducibles are available in [Google doc] and [.pdf] formats. 
  • For a hands on learning experience, teachers could have students make their own microbial fuel cell. This video shows how this could be done: How to make your own microbial fuel cell (4:58 min.).
Teaching Suggestions
  • This article and embedded videos can be used for Chemistry, Biology, Engineering & Technology,  and Earth & Environment teaching and learning related to electrochemistry, electricity generation, redox reactions and renewable energy. Concepts introduced include renewable energy sources, bacteria, cellular respiration, microbial fuel cell (MFC), battery, electrodes, anode, cathode, oxidation reaction, reduction reaction, electric current, exoelectrogens, protein carriers, mediators, genetic engineering and wastewater management.
  • After reading the article and viewing the embedded videos, teachers could have students do a Key Ideas Round Robin learning strategy to consolidation new information. Ready-to-use Key Ideas Round Robin reproducibles are available in [Google doc] and [.pdf] formats. 
  • To consolidate understanding of microbial fuel cells (MFC), teachers could have students complete a Concept Definition Web learning strategy. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [.pdf] formats. 
  • To consider the positive and negative issues related to microbial fuel cells, students could do a Pros & Cons Organizer learning strategy. Ready-to-use Pros & Cons Organizer reproducibles are available in [Google doc] and [.pdf] formats. 
  • For a hands on learning experience, teachers could have students make their own microbial fuel cell. This video shows how this could be done: How to make your own microbial fuel cell (4:58 min.).

Learn more

Microbial fuel cells & METs

See examples of MFC projects done by students from Penn State University and other researchers (universities and public schools).

Bacteria Nanowires (2014)

This YouTube video (0:41 min.) has microscope footage of bacteria sending out nanowires.

How To Set Up a Microbial Fuel Cell (2016)

This YouTube video (6:07 min.) from Science Buddies shows how to set up a soil microbial fuel cell using a Microbial Fuel Cell kit which can be purchased from Home Science Tools.

References

Alternative Energy. (n.d.). What are microbial fuel cells? 

Joseph, M., Krishnaraj, N., Shanmugam, & Perumal. (2018, July 5). Biofilm engineering approaches for improving the performance of microbial fuel cells and bioelectrochemical systems. Frontiers in Engineering.

Logan, B. E. (n.d.). Microbial fuel cells. Pennsylvania State University.

Mercer, J. (n.d.). Microbial fuel cells: Generating power from waste. University of Southern California.

Nave, R. (n.d.). Cellular respiration. Georgia State University.

Zhou, M., Wang, H., Hassett, D. J., & Gu, T. (2013). Recent advances in microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) for wastewater treatment, bioenergy and bioproducts. Journal of Chemical and Technology & Biotechnology, 88(4). DOI: 10.1002/jctb.4004