Project Update 2: Build a Basic Battery to Better Brighten our Burgeoning Futures
To better understand our project, we decided to make a simpler battery using just bacteria and freshwater. This generated a half a volt of electricity, along with a very weak current. We were hoping to power a small LED with it, but alas! It could not be done.
The battery was designed according to specifications from: https://www.treehugger.com/slideshows/gadgets/make-microbial-fuel-cell/
The basic battery was a fairly standard two-part system, an anode and cathode, separated by a membrane of agar and salt (agar is a gelatin-like material that allows certain materials to pass through it, such as water and some small ions, but not larger molecules).
The anode consisted of char cloth wrapped in a wire mesh. Char cloth is what results when you take something high in carbon, such as a cotton shirt, and heat it at high heat with minimal airflow. The lack of oxygen prevents the cotton from burning as in a fire, and instead it smolders, until all that is left is a thin, dark cloth. This is an excellent carbon source for bacteria.
We placed the anode into a solution containing anaerobic bacteria. As suggested in the website, we obtained these bacterium from the bottom of local pond. The still water develops an oxygen-minimal environment at the bottom of the pond, and as a result, only anaerobic bacteria are capable of growth at the lowest points. The material known as "muck", essentially mud full of organic materials, is full of the anaerobic bacteria used in this experiment.
In theory, the bacteria should grow in higher concentrations on the char cloth, and, by extension, the wire cage surrounding it. The bacteria oxidize hydrogen to become hydrogen ions and electrons. When connected to a cathode, this generates an electric current away from the bacteria.
The cathode was simple: water, with a stripped wire to connect the current attached inside.
The bacteria and water were separated by an approximately 1 cm thick wall of agar with salt. The bacteria was closed to air to encourage only the growth of anaerobic bacteria. The resulting cell produced, as we said previously, about half a volt of electricity. Ideally, as the bacteria continue to grow on the anode, the voltage and power will increase.
We hope to be able to use this battery and, once it's finished, the larger one, to help teach concepts of physics and chemistry at the greenhouse.
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| Agar membrane |
The battery was designed according to specifications from: https://www.treehugger.com/slideshows/gadgets/make-microbial-fuel-cell/
The basic battery was a fairly standard two-part system, an anode and cathode, separated by a membrane of agar and salt (agar is a gelatin-like material that allows certain materials to pass through it, such as water and some small ions, but not larger molecules).
The anode consisted of char cloth wrapped in a wire mesh. Char cloth is what results when you take something high in carbon, such as a cotton shirt, and heat it at high heat with minimal airflow. The lack of oxygen prevents the cotton from burning as in a fire, and instead it smolders, until all that is left is a thin, dark cloth. This is an excellent carbon source for bacteria.
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| Finished char cloth, inside the metal container (tuna can) used for the heat reaction |
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| Muck containing anaerobic bacteria, found at the bottom of a pond in the greenhouse |
In theory, the bacteria should grow in higher concentrations on the char cloth, and, by extension, the wire cage surrounding it. The bacteria oxidize hydrogen to become hydrogen ions and electrons. When connected to a cathode, this generates an electric current away from the bacteria.
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| The simple battery with a voltmeter measuring .532V |
The bacteria and water were separated by an approximately 1 cm thick wall of agar with salt. The bacteria was closed to air to encourage only the growth of anaerobic bacteria. The resulting cell produced, as we said previously, about half a volt of electricity. Ideally, as the bacteria continue to grow on the anode, the voltage and power will increase.
We hope to be able to use this battery and, once it's finished, the larger one, to help teach concepts of physics and chemistry at the greenhouse.
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