Sunday, October 13, 2013

Microbial Fuel Cell

On October 4th 2013 I began an experimenting with Microbial Fuel Cells.   My initial experiment consisted of a piece of carbon fiber cloth 36” x 4” which I placed in the water of my aquaponic system.  The bacteria grew on this cloth.  After nine days  I measured the voltage at .97 millivolt (mv) using a stainless steel cathode of approximately 6"x8" .   

http://backyardaquaponics.com/forum/viewtopic.php?f=31&t=17566&p=416193#p416193

While there are some similarities Microbial Fuel Cells are not the same as a BEAMR (BioElectrochemically Assisted Microbial Reactor) which is basically a Hydroxy gas generator.   

Several years ago I was very involved with the creation of Hydroxy gas.  Commonly known as HHO or Browns Gas.  By using electrolysis and electrolyte such as KOH (Potassium Hydroxide)  water is separated into hydrogen (H2) and oxygen (O2) in a 2:1 molar ratio.  These two gases violently wish to be reunited and all it takes is a spark.  This gas has some good applications, but it requires more power to create the hydroxy gas than the gas will return as a fuel source.  Some people have found benefit when injected along with fuel into engines that do not have
I mention this because you may find this technique while researching Microbial Fuel Cells and fall victim to the misguided ideas surrounding the creation of hydroxy gas.  

Microbial Fuel Cells are batteries created by the energy produced by the bacteria.  I can't say it any better than what has been written on Wikipedia so I will quote the entire first paragraph.

"A microbial fuel cell (MFC) or biological fuel cell is a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature. MFCs can be grouped into two general categories, those that use a mediator and those that are mediator-less. The first MFCs, demonstrated in the early 20th century, used a mediator, this is a chemical that transfers electrons from the bacteria in the cell to the anode. Mediator-less MFCs are a more recent development dating to the 1970s; in this type of MFC bacteria in mediator-less MFCs typically have electrochemically active redox proteins such as cytochromes on their outer membrane that can transfer electrons directly to the anode.[1] Since the turn of the 21st century MFCs have started to find a commercial use in the treatment of wastewate"

A little more research indicates that a MFC (Microbial Fuel Cell) must use anaerobic conditions. In aerobic conditions bacteria are free to use near by oxygen for the electron they wish to transfer. The anaerobic condition leaves only the cathode exposed to available electrons from oxygen. This creates the electrical difference between the anode and the cathode.

But I did measure a very small voltage of  97 mv on Oct 12 2013, so maybe maybe the process would be better in an anaerobic condition, but still prove viable in aerobic conditions. I'll come back to this in a few weeks and post the results.  It may improve as the bacteria continues to grow on the cloth.

It was just two days ago that I measured 97 mv... I tested the voltage again today Oct 14 2013 and found that if I moved the cathode closer to the anode I could get 300 mv!









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