Microbial Fuel Cell

[mathscience13]

Good afternoon!
I'm starting a project about how the amount of sugar will affect the amount of electricity produced by bacteria in a microbial fuel cell. I've tried to research about this topic, but I haven't gotten an answer so far. My question is that how does sugar help produce more electricity, is it because the bacteria in soil will consume sugar, and they will reproduce more, as a result, more electricity will be produced? Or does it have to do with the structure of sugar? Also, do you have any suggestions regarding to how much sugar would be the ideal amount of sugar for me to add to soil and why that would be ideal. I have 3 levels of independent variable and one is the control, so it would be great if you could let me know if you have any suggestions regarding to my research. I would really appreciate it!
Thank you so much for your help

[norman40]

Hi mathscience13,

I'm assuming that you are working on the project described here:

https://www.sciencebuddies.org/science- ... ll#summary

As you pointed out, it's reasonable to expect that adding sugar would result in more bacteria and more electricity from the fuel cell. The aim of the project above is to compare electrical outputs and bacterial colony sizes from two substrates (with and without sugar).

The project procedure describes an appropriate amount of sugar to be added to the cell. If you want to expand the experiment to include two other sugar levels you could try half and 1.5 times the amount mentioned in the project.

I hope this helps. Please ask again if you have more questions.

A. Norman

[mathscience13]

Hey again!
Would you think 4 and 16 grams of sugar would be too much for the amount of sugar added? Because the half seems a bit small in amount. I would really appreciate it if you could help me with that. Also, would you think it would cost a lot of money to do 25 repeated trials for each group because that is required. Is there anyway we can make these microbial fuel cells in smaller containers to reduce the cost somehow? I would greatly appreciate it if you could answer my question because I need to write a procedure due very soon, and I'm really needing the help right now.
Thanks!

[norman40]

Hi mathscience13,

The project procedure referenced in my previous post calls for 0.5 g of sugar (in 10 mL of water) to be added to the fuel cell. And I presume that this amount of sugar is enough to produce a measurable effect. Adding 4 g or 16 g of sugar may be too much. My suggestion is to try small increments around the 0.5 g indicated in the project procedure. For example you might try 0.25, 0.5 and 0.75 g or 0.5, 1.0 and 1.5 g for your sugar additions.

Are you planning to complete 25 trials of the entire experiment? Doing so would take quite a bit of time. Because it takes several days for the voltage to stabilize in the fuel cell you'd need a large number of fuel cells in progress to complete the work within a reasonable time.

The microbial fuel cell kit recommended in the project procedure costs $79.95 and comes with two cells. If you wanted to have more than two cells, a “classroom pack” is available for $299.99 that includes 10 cells:

https://www.magicalmicrobes.com/collect ... 7226103753

I am not aware of a microbial fuel cell with a smaller container.

You might consider scaling back your replicate trials and/or the number of sugar levels in your experiment. For example, testing two sugar levels would provide information about cell output variation with the amount of sugar. And if you repeated the experiment once or twice (and observed the trends) you'd have confidence in your results.

I hope this helps. Please ask again if you have more questions.

A. Norman

[mathscience13]

Hi again!
For the introduction of my project which is the effect of sugar on the amount of electricity produced by bacteria, I have an issue with finding the reason why I chose my levels of the independent variable. When doing my project, I used the previous advice that you gave to me and used .5 and 1.5 as my experimental groups, however, I cannot find the reason why those increments should be chosen. I would really appreciate it if you could help me out because my final paper is due very soon, and I have no clue what to do because the reason for choosing the independent variable levels is very important. This would be a great help to me. Thank you so much for your time and help!

[norman40]

Hi mathscience13,

Choice of independent variable levels is important. When planning an experiment, scientists conduct background research to help determine levels that may result in observable responses in the dependent variables. Sometimes preliminary experiments are conducted to establish appropriate levels for independent variables.

Your project procedure specifies 0.5 g of sugar (in 10 mL of water) because that level of addition is likely to produce observable effects in the microbe colony count and output from the fuel cell.

Large sugar additions could disturb the fuel cell electrodes or harm the microbes. So a higher level of sugar addition should be small enough to avoid these issues. And the higher sugar level must dissolve in 10 mL of water so that the water addition to the fuel cell is the same as for the lower sugar level. But the higher level should be different enough from the lower level to produce a change in the fuel cell.

Doubling (or tripling) the sugar addition (to 1.0 g or 1.5 g) might be expected to produce effects that are different from the lower level of sugar addition (0.5 g). And these amounts of sugar will easily dissolve in 10 mL of water.

I hope this helps. Please ask again if you have more questions.

A. Norman

[mathscience13]

Hi,
That helped a lot. I greatly appreciate the time and effort you put into this answer. Thank you so so much!!