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How Does Temperature affect the Amount of Electricity produced by a MFC

Microbial Fuel Cells (MFCs) produce electricity from electrogenic bacteria. I wanted to see how these MFCs would react to the different temperatures and see if the amount of electricity generated would change.
Justin Tan
Grade 6

Hypothesis

My hypothesis is that temperature does affect the amount of electricity produced by a Microbial Fuel Cell (MFC). When there is higher temperature, bacteria will reproduce faster. The more bacteria there is, the more electricity will be produced.

Research

How does a Microbial Fuel Cell (MFC) work?

Electrogenic bacteria can be found in many places including our regular garden soil. This special bacteria in the soil around the anode in the MFC consume the nutrients in the soil. As a result, these electrogenic bacteria then secrete electrons. These electrons are then transferred onto the anode. All the electrons then flow through a wire into the blinker circuit. The flow of these electrons is also known as electricity.  At the blinker circuit, they will make an LED blink. After that, they travel to the cathode and the process is finished.

When there is more bacteria, more electrons are released and more electricity is generated. The rate that the LED blinks indicates how much electricity is being produced.

How does temperature affect the growth of bacteria population?

According to the United States Department of Agriculture, the number of bacteria doubles in as little as 20 minutes with temperatures between 4 degrees celsius and 60 degrees celsius. This is often referred to as the Danger Zone. Therefore, a MFC in a warmer environment should produce more electricity. 

 

Variables

Controlled Variables:

  • Type of mud used

  • Amount of mud used

  • Time I built my Microbial Fuel Cells (MFCs)

  • Materials used to build the MFCs

  • Time I took my readings daily


Manipulated Variables: 

  • Where I placed the MFC

  • Different temperatures I placed the MFCs in


Responding Variables:

  • Amount of electricity produced by the MFCs

Procedure

Building the Microbial Fuel Cell (MFC)

To start off my experiment, I built five MFCs. When I built the MFCs, I prepared all the mud together at the same time. This is to make sure that the mud mixture was identical for all MFCs. I also ensured the same amount of mud was added to each MFC.

 

The next step was to put the MFCs under different temperatures. I selected five different places.

  • Unit 1 is in my living room where the temperature was constant at 20 degrees celsius.

  • Unit 2 is in my garage where the temperature varied between 5 degrees clesius and -5 degrees celsius.

  • Unit 3 is in my basement where the temperature was constant at around 16 degrees celsius.

  • Unit 4 is in my furnace where the temperature was constant at around 10 degrees celsius.

  • Unit 5 is in my shed where the temperature was not constant and ranged between -20 degrees celsius to -40 degrees celsius.

 

After I placed them there, I would take 3 readings per day, one at 9 am, one at 4 pm and another at 9 pm. I measured the amount of electricity produced by each MFC by checking how fast the LED blinked per minute. I also recorded the temperature of each MFC everytime using a thermal camera. I recorded all this data into my log book.

 

Observations

I found out that the Microbial Fuel Cell (MFC) outside had ice on top of the cathode

  • This means that the hydrogen in the mud would not be able to reach the oxygen

  • This would slow down the speed of the bacteria reproducing

  • There would be less electricity produced

Temperature does affect the amount of electricity produced by a MFC

  • After experiement, brought the outside unit in

  • Started to blink

  • Shows the temperature was affecting the amount of electricity produced.

Analysis

Unit 1 produced the most electricity.

  • This is expected because it was placed in a warm temperature which was in the Danger Zone throughout the whole day

Unit 2 and Unit 5 did not produce any electricity.

  • This is expected beacause they would only be in the Danger Zone in the day sometimes

  • It would not be in the Danger Zone at night

  • As a result, the bacteria growth was much slower

Unit 3 produced the second most amount of electricity.

  • This is because it was placed in a slightly colder temperature than Unit 1

  • It was still in the Danger Zone throughout the whole day though

  • Therefore the bacteria growth was slightly slower

Unit 4 produced the third most amount of electricity.

  • This is because it was placed in an even colder temperature than Unit 3

  • It was mostly in the Danger Zone thorughout the day and night

  • This is expected that the bacteria growth is slower

 

Conclusion

After my experiment, I can conclude that temperature does affect the amount of electricity produced by a Microbial Fuel Cell (MFC).

  • I learnt that warmer temperatures help the MFCs produce more electricity

  • Last, I learnt that temperatures below 0 degrees prevents the MFC from producing electricity

 

Application

National Aeronautics Space Administration (NASA)

Organizations including NASA are testing how the electrogenic bacteria will grow in space. They are testing to see if the bacteria will produce more or less electricity. They also want to see if the bacteria will even reproduce.

University of Calgary (UofC)

The University of Calgary is looking how these Microbial Fuel Cells (MFCs) can be used at municipal waste water treatment plants. They can be used to generate electricity from the waste in the water. Less electricity would be needed to operate these plants and it could even start producing electricity.

Sources Of Error

  • First, I could have taken these readings for a longer duration of time to see how they react with the different seasons

  • I could try putting the Microbial Fuel Cells in different places including the fridge which is constant at around 2 degrees celsius

  • I could try to be more precise when taking my readings and take them at the exact same time everyday

 

Acknowledgement

Kelvin Tan | Helped with buying materials

Jennifer Secord | Organized the school science fair

Iain Hotzel | Gave feedback on project