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Microbial Cells

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I have a small microbial cell set up, its based on a demo from the journal of biological education. They use a bacteria that isnt so easy to source in the UK, so i decided to try a few others out.

The target voltage for a 1ltr cell is roughly 0.8V, the last batch i used bakers yeast. Looking at the numbers from the logger it seems Yeast can put out 1.2V, now i confess this was a test of the set up and not really intended as a run, both electrodes are bog standard graphite. The load was by resistor and roughly 60mA, the figure wasnt picked for any particular reason.

The cell ran for two weeks as i didnt get time to do much with it, but looking at the readings from the file, it seems the cell easily held its own over two weeks, but there is a sharp drop at the end, likely lack of food or polluted because i wasnt looking after it.

Anyone else played with Microbial cells? I notice in one journal they got a new membrane material that is said to match a hydrogen cell, but really scant info at the moment, i could only get the abstract.
One reason for the interest is a phenomenon seen on various electrodes in AD systems that give false readings due to microbes attaching to them. So i was looking at a solution to this and got interested in them. Not sure where it will lead but thinking about the size of some AD systems, there might be some merit in them. I am using a energy harvesting board (will link in a min) that runs a 32bit Arm Cortex 3 processor as the main data logger and control system for a small research AD system.

I am about to try and power it from a microbial cell, before people jump on this take a look at the following videos. In my own cell i have used a different set of home made electrodes, but same principle. The harvesting kit is exactly the same as one of the ones i am using for this (wurth one), not that one of the energy sources runs from as little as 20mV to power the micro dev kit that comes with it (same dev board i am using to run the AD system).

The vid on the actual microbe cell has an interesting bit at the end, they dont show you inside unfortunately, but an email to them got a reply saying look careful at end and you should see the cells inside. They wouldnt tell me how many cells is in the end container, but its got to be alot, having said that the room is about the same size as a normal mid size AD system. So it would be interesting to build a few simple cells and see what they can do.

The other videos are on the energy kit webpage, not great info but shows what the various sources can do and shows the micro board being powered by them, one thing however.... They say the solar cell on the board works in low light, TBH the one in my kit is exactly the same and dosnt work as well, but the other sources do work really well.

This one wasnt out when i got my kit! But man its some kit!! Maybe if i earn enough this summer i will get one, take a look at it as its really some bit of kit.

This is my one

videos near page bottom. Anyone interested in long term field data loggers might find it useful, I will go dig out the datasheets for the chips, I know somewhere all the boards have full schematics, so making a battery free field logger shouldnt be too hard, the min voltage is 20mV, note a single small tub used as a microbe cell can produce 200mV+ easily, I have had over 1V from microbe cells but they are not really long term viable at the moment and need daily maintenance.
Well interesting find video wise, i am tracking down the papers at the moment. I doubt many are interested in this (fair enough) but it opens some very interesting avenues for continuous flow reactors.
Its a long thread and the focus isnt so much about the electric produced, but the figures given for sludge removal and especially heavy and precious metals recovery are pretty staggering. As a final free energy (almost) clean up stage, it would make a fantastic final chamber in a multi chamber system.

I am tempted to empty a couple of my reactors and look into this, oddly he gets best results using material thats structurally similar to what i use, he uses very high temps to get it, i use drift wood and lower temps for the bio char, but the pore sizes look about the same. I am trying to find contact details for him. Anyway maybe one day in the future as this tech takes off, a google lander will find all this and it might be useful, i appreciate its a highly specialized area.

I will also post some the details on the energy harvesting equipment from what was linear technology, anyone know what happened to all there app notes??

Note when using these cells you get CO2 not methane, hence being a end stage digester unit. CO2 is ot the bogey man its made out to be, in AD systems it has many uses, even at the very end of the process it can be used to great effect if dissolved in water and fed hydroponically to plant roots of high value crops.

Methane itself is from CO2 and H2 reactions, so the CO2 produced can be recycled back into the system if using a continuous cycle system. This is sort of the area i mess with in the lab, if it paid the bills its what i would do full time!

Funny by the time i am 40-50 this will be common tech powering most homes...
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A rare beast! open access paper on MC's, i havnt read all of this one as i think its mainly a review, but might be of interest. Its certainly one way to desludge a AD in a continuous system.

Having read much of the above paper i would like to add some comments.

Despite its date (2015) alot of the information and data tables are woefully outdated, it is mentioned within the paper that some of the tables have been taken from X or Y paper, on checking dates and the figures given these are outdated by a wide margin.

Also the paper uses meter square often but dosnt always give the context, for example when talking about Anode surface area a square meter should in this context mean surface area of the entire substrate. So a square meter in this sense could be as small as 1cm when you consider the porosity of the material.

In other areas they are in fact speaking about the plate area! So i am sorry its a bit confusing, the main problem is its open access, meaning we can share and post it without a publisher going for your throat.

Better papers exist with much more up to date data, unfortunately only the abstract can be shared publicly. Modern abstracts (IMHO) give little information and miss the entire point of there existence. But apart from that :D its useful :D

Oh one last grumble.....Platinum giving 6W per square meter does not take into account platinum poisons the substrate.
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So what use are microbial cells? Well originally and to a greater extent even now, they were looked at as a way to generate electricity. But turns out they are most certainly not one trick ponies! Most research is still around energy production, most research is still in uni labs, the odd mad man shed and a few some scale companies.

lets start with the obvious, electric production.
On the face of it they dot produce much, but most people misread or dont make the mental leap from the figures to the potential. A good microbe cell is way more powerful and provide alot more energy than modern batteries! I will come back to that statement in a bit and back it up with the evidence. The thing is most cells are copies from old lab experiments, these used single anode plates to study the energy density. so you tube is full of microbe cells with a single Anode.

What the people who make these videos fail to understand is, in a two chamber cell (anaerobic/aerobic) there is no reason you cant use one cathode and as many anode layers as you like. The caveat being you have to have at least 3-6mm of 'mud' between each plate, so best done in a tube with the Anodes laid horizontal. The limit then becomes how much oxygen you can shove into the cathode side, doing this can give some very big energy potentials.

Downsides to this?

You will literally eat more of the sludge than is practical to supply, although various current studies are trying to address this.

part 2 soon
I have been challenged to build a remote controlled car powered by a microbial cell!! Car might be stretching the definition somewhat with what i have in mind lol, but i will post an outline of an idea. To add to the fun, i excepted this challenge purely because i have no idea if it can be done on a tiny scale! We are talking balsa wood or similar and a brushed motor of around 1V. Remote control will be a very basic self built unit.

I will stick it in projects with some pics of the kind of thing i have in mind. The value in trying this however, is more in the discovery of actual energy densities in microbial cells, when your pushed to the limits space and weight wise. So useful data which ever way you look at it.
This is rather an interesting project.
I keep meaning to post a update with some pics, posting pics on here is PITA so i have put it off.

I have the Bethnoic sediment (unbelievably difficult to get in the end), currently its settling and hopefully going back to being completely Anerobic. I have the microbe anode cell but its too heavy!! I will post the pic of it and give the dimensions and weight.

Anodes are not constructed yet, the salt bridge is on hold as i am looking at a slightly different technique to what i was going to use. I have some micrographs of the bacteria i had done at the uni, i cant use them because if i do i cant then use in a write up as unpublished work, but i found a couple of similar ones on google. Trust me they are really interesting, something i have never seen before, as you will see these bacteria kind of self wire themselves together!

Electronic wise i am going to work on that while i wait for the sediment O2 content to drop more, its pretty anaerobic already, but once its in the cell i cant mess with it much, so before it goes in i have to be sure its not dying off.

Tricky bit might the voltage, the current density is good, but i dont know if multiple anodes in a single separated cell, will act as a single anode with more current, or as multiple anodes with a better voltage, if its single the voltage is going to be around 0.9V. Which is awkward to boost. I should have gone with a different cell construction, but you will see why i chose what i did when i post up next.
These are not the pics i wanted to post, i use adobe lightroom to catalog my pics, unfortunately i made a mistake and ended up scanning my entire network for pics!! So lightroom has a massive catalog of icons etc and is now useless to me!! I need to go through and delete the catalogs then rescan... or put another way i cant find them at the moment.

However the following picture isnt the same bacteria, but its a genetically modified one, what struck me however is the way the bacteria connect is exactly the same as you seen on the Anode of the cell. Whats curious with a microbe cell is the bacteria dont build up in a layer, they stay as a single layer. What you witness over time is the 'mud' is consumed, which is what interest me rather than electric generation, it is a really useful way to clear sediment from a AD digester and produce a useful waste product (electric).

The amount of electric on a full sized system is a reasonable amount to be useful, especially as the primary function is to get the sediment consumed so you dont need to empty the reactor. In a continuous flow system you want to avoid having to clean out the reactor as much as you can.

Weight has beaten me at the moment, the small cell i agreed to use is thick acrylic with a top that seals and micro port holes in the side, it would have been ideal for this, but its built for special high pressure reactions and considering its size its really heavy for what it is.

So i am negotiating to use something else a little bigger but alot lighter, its likely to be roughly the same volume of sediment, but the shap is a bit different and its harder to seal and attach a proton bridge too. I wont be using nafion for the proton film (way too expensive) but i am looking into using HCL treated Alginate for the bridge.

Often e.Coli in a broth is made into a agar bridge, but it takes ages and isnt going to be good enough for this, same with the terracotta type salt bridges, these tend to let oxygen into the Anode half of the cell. I got the alginate idea from doing microbe and yeast beads with it, if you treat them with a chloride then the outside forms a permeable skin. No ide if it will yet but i have one in the making.

Motors are down to a choice between one of two small 1V motors, no grunt at all in them, but with a toy plastic wind up helicopter gearbox, they should be able to make the car move, geriatric snail with a walking frame pace is fine :D. The micro and radio set up is all ultra low power and the board to get a decent voltage is a choice between two linear tech energy harvesting boards. I have a number of 2F super caps that are pretty small, so i will add some to the cap bank.

I dont think its cheating to store the microbe cell energy for boosting the transceiver etc when needed, seeing as all the power is from the cell itself. I gave all my balsa wood away the other week, so i am using a light stiff (ish) foam for the frame of the car. When i can be bothered i will go through the torture of taking pics and uploading them once i have messed around and screen shot so they fit the dismal upload limit.

Or i might stick the pics on my server and just link to them here. The sediment container was dropping the oxygen off nicely, then i got a small spike in Oxygen!! Small panic until i found out that apparently these types of sediments often have a spike in O2 just before the microbes we want start to take over, so with luck the cell might be ready to transfer the sediment soon.

The transfer is the worse part for me, i am going to use a glove box and because i am tight i will flush out with Butane and use that as my oxygen free atmosphere. Butane shouldnt harm the microbes (famous last words).
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