Soil-Based Microbial Fuel Cells

[Crazy_Mad_Scientist]

Hello,

I am currently in the process of developing my science fair proposal, and I'm kind of confused with soil-based and benthic mud microbial fuel cells. Is there a difference in their constructions? Do I have to build a different kind of fuel cell for soil-based samples? If so, are there any tutorials online for it? I'm hoping that I can simply use soil samples in the common tutorials you find on the internet, such as this one:
https://www.sciencebuddies.org/science- ... p026.shtml.
Please let me know if there actually will be a difference if I use benthic mud samples or soil samples. I'm worried that soil bacteria will generate less electricity.

Thank you!

[donnahardy2]

Hi,

You have picked a very interesting and challenging topic for your science project. The project link you provided from this website includes a kit that helps avoid construction and leaking problems involved with making your own fuel cell.
The molecular basis of the microbial fuel cell is electron transfer by anaerobic bacteria that use something other than oxygen as an electron acceptor in cell respiration to produce energy. You can find anaerobic bacteria in a rich organic soil sample or in the soil at the bottom of a stream or lake, so you could use either as a source of bacteria with equally good results.

I recommend that you do a search on the topic of anaerobic respiration so you will become an expert on the topic; also do check out the bibliography from the background section of the project guide.

What experiment are you thinking about doing?

Please let me know if you have any other questions.

Donna Hardy

[Crazy_Mad_Scientist]

Thanks for the quick reply!

I'm working on an advanced project so I can go to CWSF again (although currently without a mentor and with limited resources), so I don't want to be using a kit to make my microbial fuel cell . Yes I am currently doing research on how the fuel cell works.

I'm not sure where rich soil can be found? I am planning to gather soil near a river but not at the bottom of it where lots of anaerobic bacteria live... I also read that bacteria in soil are mostly aerobic. Do you think this will affect my results? I heard that they can still undergo anaerobic respiration though.

My experiment will probably be dealing with bacteria that can absorb heavy metals /other pollutants in water in a microbial fuel cell. So I will be looking at bacteria strains from different locations that can produce the highest voltage and decontaminate the most pollutants from water (such as heavy metals and turbidity). I will then isolate the top three strains and send them for sequencing? Hopefully if I have time, I can compare the DNA on Blast.

Thank you!

Crazy_Mad_Scientist

[Crazy_Mad_Scientist]

I just came across the Wikipedia page on microbial fuel cells, and it stated that the construction of the soil-based cell was different than the other 2 chambered cell using sludge. Is it actually necessary to change the constructions?

Thanks again

[donnahardy2]

Hi,

Thanks for the update. I have provided advice on MFC's in the past and was not aware there was a difference in MRC design with different soil sources. There might be a difference in specific species from different soil sources, but there should be anaerobic bacteria in any type of soil sample.

Your project idea is intriguing. I have not seen a project on cloning the MRC bacteria before.

I will check the references on the Wikipedia article and get back to you with an explanation within a day.

Donna

[donnahardy2]

Hi,

I checked out the Wikipedia article, and here is my interpretation of the information in the section titled “soil based.”

The first paragraph describes a basic MFC, which is based on soil microorganisms that transfer electrons to the anode electrode, which is anaerobic. The electrons are transferred to the cathode electrode, which is exposed to oxygen. The transfer of electrons creates the current that you can measure. This is a universal description that applies to all MFC’s.

The second paragraph describes a design for a MFC where the anaerobic and aerobic sections of the MFC are not physically divided into two chambers The reference for this paragraph is the instruction manual for an education kit that you can purchase. The directions say you can use any type of soil.

http://www.mudwatt.com/pages/how-mudwatt-works

The third paragraph describes a MFC design that allows flow of wastewater through the anaerobic chamber. This type of MFC is called a sediment microbial fuel cell, but the mechanism is the same as other MFC’s; the microbes transfer the electrons to the anode electrode, which then flow to the cathode electrode. The aerobic and anaerobic chambers appear to be divided in this design. The literature reference for this paragraph is a review article from a scientific journal. I recommend reading this article and including it your literature cited section.

http://pubs.rsc.org/en/content/articlep ... c5ew00020c

The last paragraph describes an application of a SMFC for charging a battery and a desalination application.

So, the information appears to present different designs for MFC’s, but I could not find any information that showed that different soil types require different designs. You should be able to pick any design that you want to make and then use any type of soil. The anaerobic conditions in the anode chamber along with a suitable food source will naturally allow selection of anaerobic bacteria in the soil. You can pick any design you want to make.

I like your idea of working on heavy metal remediation. If you include a specific metal in your MFC as an electron acceptor, the metal will be reduced to a different form using the electroactive microorganisms. For example, here is a reference that describes the recovery of copper and energy from a solution of copper sulfate.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4473641/

Is there a specific metal contamination problem in your local area that you would like to investigate? This would make an excellent topic for your project.

How much time do you have to complete your project? You will probably want to run your MFC for at least 2-4 weeks(longer is better), so you won’t be able to compare too many soil sources, unless you have multiple MFC’s.

Do you have a specific MFC design that you would like to use? I recommend focusing on this part of the project after you have finalized your research question:

https://www.sciencebuddies.org/science- ... ndex.shtml

Let me know what you decide to do.

Donna

[Crazy_Mad_Scientist]

Hi Donna,

Thanks a lot for the explanation! I think I understand the terminology and concepts a lot better now. I think I will go with a modified version of the Science Buddies two-chambered microbial fuel cell design, and hopefully construct two to three cells at a time so that I can conduct multiple trials.

There is a local garden that is apparently contaminated with lots of heavy metals:
http://www.cbc.ca/news/canada/british-c ... -1.2857662

Hopefully I can obtain some soil samples there and beside the Fraser river, since their may be heavy metal contamination at those sites, thus harboring mutated bacteria capable of surviving high concentrations of the metals.

I don't think that there is a specific site I want to investigate. I'll just be measuring 3-5 different heavy metal concentrations throughout the experiment. Do you think that collecting multiple samples every few days is a good idea? I'm worried that opening the lid to collect samples will disrupt anaerobic bacteria (because oxygen is being introduced), and that the voltage will go down due to less bacteria present in the cell... Should I isolate the bacteria later on and conduct tests on them afterwards instead?

I have plenty of time to conduct the experiments, since district fair is in March and regional fair is in April. However I still want to complete my first trial before February since that is the school science fair.

This year I want to conduct an experiment without using equipment from a lab (except when identifying bacteria and sequencing Dna). This way I can construct all the equipment I need at home. I already have plans to make an arduino-controlled incubator when isolating the bacteria on petri dishes.

I greatly appreciate your help Thanks Donna!

[donnahardy2]

Hi CRazy_Mad_Scientist,

Excellent. Your project question could be, “Can a MFC be used to remove lead from contaminated soil?” or something similar. Do think about your project question to be as this will determine the details of your experiment.

Your project will more dramatic and focused if you concentrate on just one problem, such as lead contamination.. It is not possible to solve all environmental contamination problems with one experiment so you should not try to do multiple metals. The presentation will be very effective if you can show how to solve the one local contamination problem.
The best source of lead-reducing bacteria should be in the contaminated soil itself, if you can get a sample from the garden soil. The bacteria in the lead-contaminated soil should be enriched for species that have been growing in the presence of the Pb. Perhaps you can find a suitable carbon source to add to encourage them to grow faster.

I am have trouble searching for articles on lead/Pb as this seems to be confusing to Google. I’ll work on this more tomorrow, but see what you can find also. You will need a method to measure Pb.

You should be able to contact a local mentor at UBC. Try contacting the researcher mentioned in the article to see if you can get any additional advice on this topic. It sounds like you are thinking about all of the important details needed for a project, but it’s always good to have more expert advice if possible.

Your MFC design sounds like it will work well. The key to achieving high current in a MFC is the surface area of the anode electrode and no leaks. The anaerobic bacteria will form a biofilm on the electrode surface to transfer electrons as they grow, so a higher surface area will work better.

This is definitely a project you can do at home, except for the cloning, of course. However, do you have a location that will maintain a constant temperature over time, preferably as high as possible? At least 22 degrees Centigrade, but up to 30 would work well. The growth of bacteria will depend on the temperature and you will want to compare results of experiments done over time. Anaerobic bacteria smell terrible as they are growing, so this is not something you can do inside the house.

Donna

[Crazy_Mad_Scientist]

Hi Donna,

Yes, my project question will be something similar to that. Most studies I read about bio remediation always test the presence of several metals. Do you think that testing simply one metal will make my project too simple?

I did some research last night on Pb quantification:
https://www.researchgate.net/post/What_ ... oscope_AAS

He stated that the Chaney/Mielke extraction/analysis can be used. However I would need to get my hands on some equipment from a local university. I can also use qualitative chemical reactions, but they won't indicate the concentrations... If I'm using only testing for 1 metal, I can measure the byproducts that form while the bacteria metabolize the metals.

I think that I will conduct the heavy metal remediating experiments separately after getting the voltage and bacteria from the microbial fuel cells. It's too much of a risk to open the lid, like you said.

I was thinking that I would only construct the microbial fuel cells in my basement first, and then add the soil in my garage . I can set up a heater in the garage to maintain 25-30 degrees Celsius throughout the experiment.

Thank you so much Donna!

[Crazy_Mad_Scientist]

By the way my chemistry teacher can help me with some chemical reactions to detect presence of heavy metals qualitatively (with color). However I don't think that it will be useful with my project since I want to know the exact concentrations . I think I will go with my other two methods. I will do more research on atomic absorption spectroscopy and look for local labs with the spectrometer tomorrow.

Crazy_Mad_Scientist

[donnahardy2]

Hi CMS,

The wet chemistry method for lead quantitation might be suitable for your project.

The exact project question is definitely up to you and what you think you can do. My impression of what you are planning to do is that it’s going to be a huge amount of work with one metal and perhaps an overwhelming amount of work if you try to do all of the metals. In my opinion, it’s better to do an excellent job on a smaller defined problem, rather than trying solve all problems with one project.

At the science fair, you will need to get the attention of the science fair judges and convince them that you have done a significant project that might solve one of the world’s problems. The impact of trying to solve one important problem (lead contamination or something else) might be more effective than trying to solve the problem with all of the metals in one project. You can explain how your project will help to solve the problem.

If you decide to concentrate on lead, your background section can include the problems with lead contamination through history from Roman times through the present including the water contamination in Flint Michigan and the problem at your local community garden. Your project on the local community garden will show how this one important problem can be solved.

You can leave the exact project question open for the moment, but definitely decide before you start the first experiment. Do consult with your teacher on this important question and get a second opinion.

I thought of one major problem in doing a project on lead. Using a MFC fuel cell to convert soluble lead from a soil sample, which is present as Pb+2 to elemental Pb, which is not soluble, is that this would make the lead less toxic, but would not remove the potential for human toxicity because the lead would still be present in the soil. If you were processing water that was contaminated with soluble lead ions and converting them to the insoluble metal to remove them, that might help eliminate the problem. However, you do need more information on this topic so you can do a valid project. Perhaps the lead expert at UBC could provide additional advice on this question.

For your project, you will need to become an expert in microbiology, electricity, engineering, cloning, and metal chemistry.

Assuming for the moment, that you will continue to work on lead, here is some background on lead chemistry.
Here is an abstract reporting the reduction of lead dioxide in a microbial fuel cell for the purpose of producing electricity. I did not try to request the article, which should include more details, but this report seems to indicate that microorganisms can use lead as a terminal electron acceptor, which is what we expected.

https://www.researchgate.net/publicatio ... _Fuel_Cell

This article provides good background on problem of lead contamination in water

http://scholarworks.umass.edu/cgi/viewc ... t=intljssw https://en.wikipedia.org/wiki/Lead

This article had good information on lead chemistry and toxicity in humans.

http://www.luc.edu/faculty/afitch/Artic ... istics.pdf

Here is the link for information on the scientific review committee from this website. Since you will be working with unknown microorganisms and toxic metals, you may need to have prior approval from your local scientific review committee before you do your project. Do not skip this step as your project could be disqualified at the time of judging if proper approvals are not obtained before you do any experiments. Ask your teacher for help if you need more information.

Scientific review committee https://www.sciencebuddies.org/science- ... _src.shtml

Your basic project idea is excellent, but the underlying premise needs a little more discussion. Please check out the section on choosing a topic from the link this website about how to be successful at a top science competition for more comments:

https://www.sciencebuddies.org/science- ... cess.shtml

Donna

[Crazy_Mad_Scientist]

Hello Donna,

I think I can use a qualitative soil test kit that can indicate ppm concentrations of lead : http://www.leadinspector.com/learn/how-to-use/

I have been reading a number of papers concerning bio remediation of heavy metals, and I found that most studies revealed that the main mechanism behind the removal of the metals is bio adsorption. What is useful is that dead microbes can also contribute to the remediation. Here is one of the studies I read: http://file.scirp.org/pdf/ABB20120300017_83240845.pdf. However the bacteria will only be able to absorb a certain amount of metal. On the other hand, if the certain strain of bacteria I'm using can actually degrade the metal or reduce it into a less toxic form, I would need to include an experiment showing the toxicity of the "degraded" metal samples on Daphnia Magna. I can understand now why finding multiple heavy metal concentrations would be a lot of work .

In the meantime I will try to contact some UBC researchers for additional help.

Last year I researched a lot on microbiology, so I'm very familiar with isolation and microbiology techniques. However I did not learn chemistry in school yet (I think I'm going to learn it in last term or possibly in 2 years). I will hopefully do some more research on any chemistry material later on.

Thank you for the papers! They were very informative!

Last year the science fairs I attended did not require that I have my project approved by the scientific review committee. They stressed more on ethics forms. How can I find out if I need to have my project approved? I checked my fair but they didn't have any information on it, except for display safety requirements.

Thank you!

[donnahardy2]

Hi CMS,

You are welcome!

The kit looks good and would be an eady way to test lead. The only problem is that the kit is that the chemistry is not explained. For the science fair, you will need to know how this test works. It’s likely that the test is based on the formation of an insoluble sulfur compound:

http://pubs.acs.org/doi/abs/10.1021/ac3 ... ode=ancham

To find out how the test works, you can call or e-mail the company and confirm the chemical basis for the formation of the black color and explain that you need to know the chemical reaction for your science project. Also ask if there are any other metals that interfere with analysis and ask if they can suggest controls for you to use (positive and negative).

Your analysis of the literature on bioremediation is very astute. However,please remember that you don’t have to solve the entire problem of lead remediation in one science project. You are trying a completely different approach to lead remediation, which is to convert the soluble lead ions to elemental lead to reduce the toxicity. The traditional approach to lead contamination is to add phosphate, which forms a salt that has very ow solubility, and reducing the lead ions is similar, but unique.

For the science fair, you need to understand the problem of lead contamination and explain how your project fits into the big picture. Bioremediation is part of the story, but perhaps your project is a better idea that will help solve the problem more quickly and efficiently. It is true that once the Pb is converted to the elemental form, it is still present and has the potential for toxicity, however, perhaps for next year’s project you could devise a way to safety remove the Pb from soil. Pb is very dense, like gold, so perhaps you could adapt gold mining techniques to cleaning up lead-contaminated soil? You have more than enough to do this year, so don't add anything else to your project. But do think about what the next step would be if you were to continue your project.

I finally found some useful information about the toxicity of elemental lead (Pb)

https://toxnet.nlm.nih.gov/cgi-bin/sis/ ... @DOCNO+231

In a microbial fuel cell, you will be reducing the Pb+2 to elemental Pb, which is much less toxic than the lead ion because it is an insoluble solid. The colorimetric test you will be using measures soluble lead, so you should see a reduction in the lead concentration as the microbes reduce the Pb+ to Pb.

Here is an older, but excellent reference on methods of lead analysis. It explains the chemistry of lead. Since you haven’t had chemistry yet, please do read this paper and let me know if you have any questions about the chemistry. Understanding lead chemistry is important for your project.

http://www.luc.edu/faculty/afitch/Artic ... istics.pdf

Here is a recent review article that summarizes the problem with lead poisoning. I love review articles because they include information from lots of other published papers, so you can get all of the information by reading just one article. The sections from introduction through ionic mechanism of lead toxicity include important background information for your project. If you need more detail on a topic, you can check out the 102 papers in the bibliography.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3485653/

For your project, it would be excellent if you could run a control MFC using a soluble lead salt such as lead acetate or lead nitrate as the electron receptor to show that your microbes can use lead for their respiration (like humans use oxygen). Can you find out if you can get a suitable lead compound? Ask your teacher or the UBC researcher for help if you have trouble.

We need to get more information about the scientific review process. In our local science fairs in the US, we always make sure students get the required approval so if there’s no problem when they go on to higher levels of competition. Did you ask your teacher?

How are you doing on finding MFC construction materials?

Donna

[Crazy_Mad_Scientist]

Hi Donna,

Yes I will definately contact the company if I end up using the test kit . If not my science teacher is an expert at chemistry and can help me run a few qualitative tests to review presence of lead. I am not quite sure if the bacteria will undergo bioabsorption or lead reduction like you mentioned.

I can find most of the materials to construct the microbial fuel cell mentioned in science buddies, but I realized that conducting multiple cells at a time with a control will be difficult since it uses a lot of resources. I may only compare two-three souces of soil: Fraser river, contaminated garden, and the control. Do you have any suggestions for building simpler and smaller fuel cells with less supplies? Of course I could build many large dual-chambered fuel cells, but it would be kind of expensive.

I also have another problem with heating right now. I don't want to be building the mfc in my house because it would stink, but my garage would be very cold on the other hand. I can build an incubator easily but it would be hard to fit so many mfcs in one incubator. Do you have any suggestions for places to put the mfc?

I will ask my teacher about the scientific review commitee after the long weekend.

Thank you so much for your amazing help!

[donnahardy2]

Hi,

It would be sufficient to compare results of the contaminated garden soil and with one of the other soils. The presence of Pb+2 would be a controlled parameter in both cells. It would be great if you could do more, but not absolutely essential.

Bruce Logan from Penn State University has probably published more articles on the MFC than anyone else. Here is a review paper from him on MFC design:

https://www.researchgate.net/profile/Ko ... 000000.pdf

Here is a simple design that might work well if you invested in good electrodes with high surface area.

http://www.instructables.com/id/DIY-Mic ... Cell-easy/

Try to minimize junctions that require gluing. If you do have to glue pieces together, make sure you use water-resistant glue. Sprinkler pipes that are designed to be threaded together for a watertight seal seem to work well.

MFC bacteria can grow at lower temperatures, but will grow more slowly. If you can't achieve 22-30 degrees Centigrade, try for 15-20 degrees C. Again, temperature will be another one of your controlled parameters. The rate of bacterial growth generally doubles with every increase of 10 degrees Centigrade up to the maximum temperature.

Unfortunately, science projects are always done in the winter. When you write the section of the project where you explain what you would do differently if you had the chance, be sure to mention that you would do the project in the summertime.

Donna