Authors
Valère Maurice Hofstetter
Summary
Microbial Fuel Cell are usually requiring a membrane in between two chambers. The presence of a membrane makes classical MFC quite sophisticated, more expensive and somewhat cumbersome to scale up. Here I report the discovery of a one chamber and membrane less MFC based on biofilm.
It simplicity makes ideal for a wide number of applications.
Image 1
Image 2
Image 3
Image 4
Introduction
The use of fixed culture is common practice in water treatment plant. However the use of fixed culture on a support is rarely used for algae culture even at the laboratory scale. Despite the facts that it allows a higher cell density and a easier way to extract the biomass from the medium. Indeed to change the medium in a batch culture, one can simply remove the sponges and press them to extract the preconcentrated biomass. The sponges can the be reused to reseed the culture with fresh medium.
The original mono chamber MFC I made was a culture of Spirulina in a single transparent container. I called it a Spirupile for Spirulina and in reference to the French word for battery, originating from the Voltaic battery. The first characteristic is an insulating culture support with a high surface to volume ratio and that allows the contact of the biofilm all along the culture. A cheap kitchen sponge works fine. The second characteristic is two electrodes touching the sponges on top and bottom of culture flask or on both side of a flat container. Preliminary results suggest that the shape of the container directly influences electricity production in a significant manner.
Since the interest of the experiment is the energy balance, no agitation device was used. It could also potentially affect the current production of the biofilm by disrupting biofilm contact between two pieces of support . The use of an air pump or an external source of CO2 or both are not necessary but improves the culture. If used, care should be given to the support mechanical stability. However preliminary results suggest that they don't directly influences electricity production in a significant manner.
Materials
-Transparent container, a recycled bottle of 1.5 liter.
-Four regular kitchen sponges
. For the electrode two pieces of aluminum foiled and an insulated wire attached to each one.
- Spirulina standard medium
Procedure
Cut the top of the bottle.
Add the electrode at the bottom of the bottle.
Add the sponges.
Add the medium and squeeze the sponges to ensure uniform medium distribution.
Add the algae concentrated start culture.
Add the second electrode at the top.
Anticipated results
You can expect the unexpected for your multimeter.
The resistance is variable and changes upon measurement.
The polarity is variable especially at the beginning of the culture.
For a one liter culture the voltage is in range hundreds of millivolts.
The current is mainly DC but AC current is also sometimes measurable.
The surrounding electromagnetic field can affect the measurement.
Further details
The Spirupile exist in another version using a cloth instead of a sponge.
You can easily make an other version which is actually the first one I made. Just wrap a cloth around a bottle, add a wire of iron at the bottom and another at the top and connect them to insulated wire. Place the wrapped plastic bottle inside a glass jar. Filled with culture medium up to half the cloth.
The current is weaker but the voltage is quite similar to the sponge version. The polarity inversion and the presence of AC current happens quite often.
Using the cloth version of this Spirupile and a AC to DC convertor made of four diode and a capacitor, I have noticed a significant voltage drops.
However you can measure surrounding electromagnetic fields from AC current with a great sensitivity by the observation of the voltage variations. Switching an electric device nearby or even touching the outside of the glass of the jar causes a significant voltage variation.
References
I could not find anything even remotely close. If you do please send me the reference.
Advertisement
Stats
- Recommendations n/a n/a positive of 0 vote(s)
- Views 995
- Comments 0