brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Sun Dec 20, 2020 5:22 pm

Hello,

I am planning to start building my fuel cell very soon, but I was hoping to clarify a few things before.

1. In the cathode would I be pouring stream water or regular, distilled water. The ScienceBuddies procedure/guide says to use stream water, but do they both work effectively?

2. Is there any alternative I could use instead of the carbon cloth and nickel epoxy? I have watched a few videos of how people make microbial fuel cells and most of them use aluminum mesh. Would that work, and if so, would it be more efficient.

3. Do you have an idea of an approximate amount of compost (my form of nitrate in the experiment) I should add to the fuel cells? I am planning on making three fuel cells, one as the constant and the other two with different amounts of nitrate.

4. Do you have an idea of the expected outcome of voltage after adding the nitrate (simply an estimated average)? I was curious as I wanted to know what to look out for.

Thank you so much,
Brindha

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Sun Dec 20, 2020 11:03 pm

Also, to make the salt bridge solution is agar absolutely necessary? I have not been able to find any agar online that arrives in time. If I were to make the solution extra salty would that replace the need for agar?

Finally, I have one more question... I hope it's the last. Would the glass rod for stirring the salt bridge solution be absolutely necessary as well? I saw a few videos where they stirred the solution with a spoon, so would that be ok?

Thank you,
Brindha

koneill18
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby koneill18 » Mon Dec 21, 2020 5:05 pm

Hi Brindha,

I did my best to answer your questions below! I’m a biologist, so my knowledge on the physics of electricity and fuel cells is pretty limited. If you want to get a second opinion after reading my answers or if you run into more questions as you’re building the microbial fuel cell, I would recommend making a post on the Physical Sciences forum. There are a bunch of physicists and engineers over there that can probably give you much better help than I can! But here is my best shot at answering your questions:

1. It’s better to use the stream water if you can since that’s the water that the benthic mud sample is in and you want to keep things consistent. When you go to the stream to collect the mud sample, you can just collect an extra jug of water while you’re there. But if you can’t get the extra water for some reason, I think that the distilled water would probably still work.
2. Carbon cloth is usually used for fuel cells because of its good conductivity. I don’t personally know of an alternative for it, but if you find something online that someone else used in their fuel cell, I think it’s fine for you to give it a try yourself.
When you’re making the electrodes for the microbial fuel cell, you need to attach the copper wires to the carbon cloth with an adhesive that conducts electricity. Nickel epoxy is one kind of electrically conductive adhesive that’s commonly used. If you can’t get the nickel epoxy, you can do an online search for “electrically conductive adhesives” and see if something else comes up that will work for you. I’m not sure that the aluminum mesh would work as an adhesive, but if it seemed to work in the videos that you watched, you can certainly give it a try.
3. I’m not sure exactly how much compost would be ideal, but it’s important to make sure that you don’t add so much compost that it absorbs all of the liquid in the mud. As a starting place, you can try making a mud/compost mixture that’s about 10-20% compost. Science is all about experimentation, so you never really know what’s going to work the best until you try it, but this seems like a reasonable amount to start with.
4. I did an online search, and it looks like microbial fuel cells usually produce around 0.15 volts. It’s hard to say what values you’ll get after adding the compost. I would recommend checking out the research article I sent you last week and seeing what numbers those researchers got. They were also using compost to make a microbial fuel cell. It looks like they were getting a power density of about 1.278 mW/m2.
5. It’s necessary to add the agar to the salt water solution because the agar is a solidifying agent. Your salt bridge has to be a solid because the fuel cell requires a solid medium for conduction. If you can’t get agar in time, you can try using gelatin instead. I’m not sure it’ll be quite as structurally sound as the agar, but I think it’ll still get the job done.
6. I think the procedure tells you to use the glass stirring rod because glass isn’t a good conductor of heat so it won’t get hot while you’re using it to stir boiling water. Metal is a good conductor of heat, so just keep in mind that if you use a metal spoon to stir the mixture, it could get really hot.


I hope this was helpful!

brindhaaa
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Microbial Fuel Cell Clarification

Postby brindhaaa » Mon Dec 21, 2020 11:18 pm

Hello,

My name is Brindha Srivatsav and I am a 9th grader. I am a part of my school's Science Research program. For my project this year, I will be creating three microbial fuel cells of which one will be the constant, and the other two I will test different amounts of nitrate (compost) and see which amount produces the most electricity output.

For the most part, I will be following the "Waste Not, Want Not: Use a Microbial Fuel Cell to Create Electricity from Waste" ScienceBuddies project for building the MFC. A detailed explanation of my project and procedures can be found here:

https://www.sciencebuddies.org/science- ... from-waste


1. In the cathode would I be pouring stream water or regular, distilled water. The ScienceBuddies procedure/guide says to use stream water, but do they both work effectively?

2. Is there any alternative I could use instead of the carbon cloth and nickel epoxy? I have watched a few videos of how people make microbial fuel cells and most of them use solder copper wire to aluminum mesh. Would that work, and if so, would it be more efficient.

3. Do you have an idea of an approximate amount of compost (my form of nitrate in the experiment) I should add to the fuel cells? I am planning on making three fuel cells, one as the constant and the other two with different amounts of nitrate.

4. Do you have an idea of the expected outcome of voltage after adding the nitrate (simply an estimated average)? I was curious as I wanted to know what to look out for.

5. Is the carbon cloth for the electrodes a carbon fiber cloth? I found one on amazon but I am not sure if it is the right type. This is the link to it if anyone was interested in checking it out:

https://www.amazon.com/1000x300mm-Plain ... pldnSite=1

If anyone could help me with my project, it would be so helpful.

Thank you so much,
Brindha


[Administrator note: project: https://www.sciencebuddies.org/science- ... from-waste -- See materials list for the kit and for links to some of the other required items]

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Mon Dec 21, 2020 11:19 pm

Thank you! This definitely helps. I have also posted on the Physical Sciences forum.

Brindha

cmpayne
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Re: Microbial Fuel Cell Clarification

Postby cmpayne » Tue Dec 29, 2020 10:11 am

Hi Brindha,

This sounds like an exciting project. In response to your questions,

1. The solution used in the cathode needs to be conductive, which is the reason for adding salt. Stream water will contain many more impurities, including some microbes, and will likely be much more conductive than distilled water+salt. However, both should work as long as your benthic mud sample contains electron-producing microbes. Just make sure there's nothing in the water that would kill the bacteria (e.g., chlorine).

2. There appear to be several alternatives you can try. Dr. Bruce Logan has an excellent webpage with resources on building microbial fuel cells. His FAQ document discusses some alternative materials (e.g., carbon paper, carbon mesh, graphite felt, etc.). Copper wires must be sealed with a conductive epoxy to prevent corrosion by the salts in solution. The website mentions Ti wire as an alternative. I'm not sure which would be more efficient; it will depend on the resistivity.

3. I don't have a good answer for the amount of compost you will need. Compost will have a variable amount of nitrogen in it depending on how it was produced and the materials used. Here's an article discussing these effects (https://www.mdpi.com/2071-1050/7/9/12634/htm).

4. Again, this will be difficult to estimate without knowing more about your setup. I would guess in the 100 mV range or less. But that is just a guess...

5. That carbon cloth should work. The FAQ document linked above has a few additional links for acceptable carbon cloth materials.

Best of luck!
Dr. Payne

MadelineB
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby MadelineB » Tue Dec 29, 2020 3:15 pm

Hello Brindha,

As you can see, I've merged your posts into one thread so that all the experts who have been helping you can see your follow-up questions. Keeping your posts on this topic together helps to ensure that all of your follow-up questions get answered!

Thanks!
Madeline
Moderator

I am also going to cross-post this thread with the 9-12 Physical Sciences ... so experts in both forums can contribute their expertise! Best of luck with your project!

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Wed Dec 30, 2020 12:49 am

Thank you so much!

I think I am set to conduct this experiment, but the only thing I am not sure of is the amount of nitrate. Hopefully, I will be able to figure something out.

Thank you for all the help!

Brindha

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Wed Dec 30, 2020 11:14 pm

Also, I will be using natural compost from my house as a source of nitrate. Is there any foods/natural waste (orange peels, eggshells, etc.) that you know of which have high nitrate levels to use as my compost?

Thank you,
Brindha

koneill18
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby koneill18 » Thu Dec 31, 2020 10:18 am

Hi Brindha,

Here is a link to an article that talks about nitrogen-rich foods and natural waste materials that you can use for your compost. Coffee grounds, egg shells, tea bags, fruit and vegetable scraps, grass clippings, and leafy plant trimmings are all good options.

https://www.dummies.com/home-garden/green-living/nitrogen-rich-materials-for-your-compost-pile/

I hope this helps!

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Fri Jan 01, 2021 10:34 pm

Thank you!

Regarding the wire epoxy for glueing the copper wire onto the carbon cloth, I purchased this from Amazon, but I am not sure if it will work. Here is the link:

https://www.amazon.com/gp/product/B000Z ... UTF8&psc=1

I wanted to double-check that it is ok to use as opposed to a nickel epoxy or other conductive epoxy.

Also, I only found 24-gauge copper wire for the electrode, but the ScienceBuddies procedures/materials say to have a 12-gauge copper wire. Would 24-gauge still work?

Thank you,
Brindha

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Sun Jan 03, 2021 9:50 am

Also, I understand that you are not sure of how much compost (nitrate) should be used, but I am really stuck on that. Do you have any tips on how to go about finding that or any main concepts that would help me figure this out?

Thank you!


Brindha

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Sun Jan 03, 2021 5:05 pm

I received the wire glue, but it is very watery and does not seem to work. I cannot find other conductive epoxies that arrive in time since I am planning on testing the fuel cell for 3 weeks. Would the electrodes still work if I used an unconducive adhesive such as super glue, plastic adhesive, or even electrical tape?

Also, I was wondering how the nitrate would enhance the overall electricity output? Would it undergo a process that would help anaerobic respiration, or something similar to that?

Thank you,
Brindha

cmpayne
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby cmpayne » Mon Jan 04, 2021 8:54 am

Hi Brindha,

Regarding your questions...

Also, I understand that you are not sure of how much compost (nitrate) should be used, but I am really stuck on that. Do you have any tips on how to go about finding that or any main concepts that would help me figure this out?


If you choose to use compost as your nitrogen growth source, there is no way to know how much compost you will need without a chemical analysis of your compost and knowing which microbes are in your colonies. As I mentioned before, compost will have varying amounts of carbon and nitrogen compounds depending on the organic and nitrogenous materials used as food sources. You would need to approach this as another set of experiments. You could evaluate microbial growth as a function of the amount of compost added (changing only the amount of compost as a variable). Too little compost will diminish the rate of growth and too much compost will likely inhibit growth or kill the organism. Here's a link to a recent article that does just that:

https://www.nature.com/articles/s41598-020-61038-7

The article states the following:
Coin cells were assembled in open air by using graphite (15 mm) with the working electrode at the anode and 3 g of compost soil. Graphite was used as the counter electrode (cathode). Studies were carried out with five different concentrations of urea: 0.1 g/ml, 0.2 g/ml, 0.3 g/ml, 0.4 g/ml, and 0.5 g/ml. For comparison of power, the concentration of urea fuel was fixed at 0.5 g/ml in the liquid state. The dimension of the coin cell used for the experiment was that of CR2032 (30 d × 3.2 mm), and the surface area of the cell was 3.14 cm2.


Note, they added urea as additional "fuel" to the compost, but you may not need to do this. The urea just makes the fuel cell produce a higher power density. Your fuel cell is probably constructed differently, so you will still have to experiment with the amount.

Alternatively, you could add a known nitrogen concentration to your soil from a commercial such as soil activator, liquid compost extract, blood meal, etc. Again, you would need to conduct a set of experiments to determine the ideal concentration to add.

I received the wire glue, but it is very watery and does not seem to work.


Epoxies (also epoxy resins) are typically sold as two different "phases." One component is the polyepoxide precursor and the second component will be a hardener/curative agent. The later phase is probably the watery part. When you mix the polyepoxide with the hardener, the material polymerizes (gluing the materials together). This is a reaction that will give off heat, so be careful not to get it on your skin.

Taking a look at the product you purchased, it seems the two phases are in the jar together. I think you need to stir the mixture well before using it. Once you stir it together, you will need to work quickly because the polymerization reaction is usually pretty fast. The description suggests using a toothpick to apply the homogenized solution to your surfaces. It also states that it takes overnight to fully cure, so plan on leaving the wire/carbon fiber materials alone for at least 12 hours.

If that still doesn't work, you can probably use copper foil tape. You should be able to get this from any hardware store. Or if you have a local electronics/hobby store or RadioShack you should be able to find conductive adhesive there. For example...

https://www.radioshack.com/products/rad ... -wire-glue

And if none of those are available to you, you could probably get by with adding powdered graphite to some regular adhesive or super glue. Powdered graphite is also sold at all hardware stores or can be made by grinding pencil "lead" which is actually just graphite.

I hope this helps!

Best of luck,
Dr. Payne

brindhaaa
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Re: Finding a Bacteria for my Microbial Fuel Cell

Postby brindhaaa » Mon Jan 04, 2021 3:03 pm

Regarding the nitrate amount, based on your recommendations, I think I will just add different amounts of nitrate-rich compost and record my data. I read in an article that nitrate, more than carbon, helps anaerobic bacteria grow well, but I do not understand how it does that. Would you be able to give me a brief overview of the process, if you are aware of it?

Update on the wire glue: I think, as you said, the phases were just mixed into one. I applied the glue over the wire with a paintbrush and left it to dry overnight and it seems sturdy enough, so thank you for that.

Many other posts about MFCs say to use the benthic mud sample within 24 hours to keep the anaerobic bacteria alive. I am just curious, but when I put the mud into the MFC and test it for 3 weeks, how would the bacteria still survive?

Thank you so much for all the help!

Brindha


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