Science Buddies: "Ask an Expert"

How much power does this microbial fuel cell generate?
How does the power change with time?
What kind of electrical device I can run with one microbial fuel cell ?
How to feed my bacteria ?
How to do this project with waste water ?

Thank you

Hi Rimke,


It sounds like you are interested in doing this really challenging project from the Science Buddies website:

https://www.sciencebuddies.org/science- ... p026.shtml

You will need to read through the project guide to learn more about the topic, however, are some general answers to your question that should help you get started.

The amount of current and the change in current are results that you will determine from the specific microbial fuel cell that you make. You will need to measure the results to find out.

Most lab-scale MFC's produce very low current, so look for a very small electrical device such as a small light bulb or fan to run with your fuel cell. Maybe you could charge a cell phone. Or, you can graph your results of measurements made with a multimeter.

A microbial fuel cell depends on electrons that are transferred to the anode electrode by anaerobic bacteria growing as a biofilm on the electrode. The bacteria use the electrode as a terminal electron receptor at the end of respiration for energy production. You will use mud as a source of bacteria as described in the project; waste water contains small carbon molecules like organic acids that these bacteria can use as a source of energy.

If your project is due on the 26th, you will not have time to make a microbial fuel cell if you have not already made one. The bacteria take a few days to start growing.

Instead, you need to pick a really quick project from this website and perhaps save the MFC for next year.

Please post again if you have more questions.


Donna Hardy

Can you tell me approximately how much power does this microbial fuel cell generate or send me graph results because I will not probably manage to do it till deadline.
For what we are using the carbon cloth in this project, what is the purpose of carbon cloth ?

Thank you

I have forgotten to ask you about bacteria, in my city there is big river, can I collect the mud from that river ?
Can you give me advice what kind of mud I need.
And also can you explain me about that growing bacteria ?

Hi Rimke,

Collecting mud from the bottom of a big river could be dangerous. If you can find a shallow area that does not have a strong current, you could use a small bucket attached to a rope to collect a sample of mud from the bottom of the river. Otherwise, is there a small stream or a park with a small pond. If you can find a pier that goes out over the water, it would make collecting your sample easier. You want to get a sample of mud that has been covered with water for a long time, but it doesn’t have to be really deep water.

You will be putting the mud sample, which naturally contains anaerobic bacteria in the anode chamber of your MFC. The bacteria will grow and will attach to the carbon cloth, which is the electrode for the anode chamber of your MFC. The bacteria will use whatever food source is available to grow and multiple and produce energy. The current produced by the MFC reflects the metabolic rate of the bacteria.

I can’t tell you how much power your fuel cell will generate. This will depend on how well the bacteria grow. You can use a multimeter to measure current, voltage, and resistance. You can check to make sure your actual results are consistent with Ohm’s law:

http://en.wikipedia.org/wiki/Ohm's_law

And you can use these results to calculate the power generated:

http://www.csgnetwork.com/ohmslaw2.html

Let me know if there are more questions.

Donna Hardy

Today I have finished my experiment, thank you so much you are very helpful, next week I am going to have competition, wish me luck

Hi Rimke,

Good luck to you. Here is information from the Science Buddies website for the display board.

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

Let me know if you have any last minute questions.


Donna Hardy

Can we use something else instead of mud but to keep the procedure same ?

Hi Rimke,

For this project, you need a source of obligately anerobic bacteria that do not use oxygen for respiration. Mud that has been covered by water for a long time is an obvious source of this type of organism. I suppose you could also use a soil sample that has been standing in water for a while. Manure from a ruminant animal like a cow would also work, but would not be as safe to work with. Can you think of any other sources of organic material that you have available to work with?

Donna Hardy

I have a little problem, on my postere I need to put graphs, but I don't know about what. I have made one about voltage. But i have planned 3 more. Can you please help me, give me idea
Thank you

Hi Rimke,

There are two other parameters you can graph, if you have the data. Having one graph showing voltage on the y axis vs time on the x axis is a good idea. You could do similar graphs with current vs. time and power vs. time. The resistance should have been constant throughout the experiment.

Did you record the temperature variation during your experiment? If so, the temperature could explain fluctuations in the voltage/current/ and power.

Donna Hardy

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Can you explain how electrons are generated from the bacteria and then transferred from the bacteria to the electrode?

Thanks!

Hi Nancy,

Please post questions about YOUR project on a separate thread so we can keep straight which experts' answers go with which questions!

You asked how the bacteria used in a microbial fuel cell produced the electrons that create the power in the cell. If you read the Background section in this Scibuddies project you will find an explanation of the anaerobic process that accomplishes this: https://www.sciencebuddies.org/science- ... background

If you want more details of the electrical generation process, read the wiki on microbial fuel cells: http://en.wikipedia.org/wiki/Microbial_fuel_cell

Hope this helps. Post again on your own thread if you have more questions.

Good luck!

Sybee