mudwatt and bacterial batteries

[dumpa]

Hi,

I just found out about a battery that consists of an anode, cathode and mud (with bacteria and microrganisms). I want to research on this a little and find the best combo to use it as a source of energy eg. garden lamp.

any pointers?

[Brian Degger]

look up microbial fuel cell

http://en.wikipedia.org/wiki/Microbial_fuel_cell

cheers

Brian

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[Patrik]

It's called a Microbial Fuel Cell:

http://en.wikipedia.org/wiki/Microbial_fuel_cell
http://www.microbialfuelcell.org/

That second link has lots of great DIY designs for how to build a
"proper" MFC. The Mudwatt is a great educational tool to demonstrate
the principle, but it has some significant drawbacks if you want to
generate real energy. The main problem is that it doesn't use a proton
exchange membrane to separate the electrons and protons that will
generate the electricity for you. Instead, it just has a jar of mud
between the electrodes, which will result in a large internal
resistance, and a very small trickle of useful current. Actually, one
of the more useful parts of the Mudwatt in my opinion is the little
circuit on top that accumulates that small trickle of electricity, and
uses it to flash an LED.

Instead of an expensive proton exchange membrane, most DIY MFCs use
something called a salt bridge between the anode and cathode chamber,
basically just a tube filled with salty jello. Much more efficient
than a column of mud.

[Thomas Stowe]

Maybe you should try to develop something more conductive and possibly porous for the bacteria to live in, with or without the mud. I know in some places they really are using these batteries (3rd world problems, eh?) so it may be quite beneficial.

Thomas C. Stowe

Email stowe....@gmail.com 

Texas Computer Services http://www.txpcservices.com

Portfolio/VCard/Resume/Blog http://www.thomasstowe.info

Phone +1-210-704-7289

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[John Griessen]

On 09/23/2011 01:22 AM, Thomas Stowe wrote:
> Maybe you should try to develop something more conductive and possibly porous for the bacteria to live in, with or without the mud.

Might the same bacteria that set up life cycles in sand filters for ponds
be good for this?

[Simon Quellen Field]

The bacteria in a good under-gravel filter will be primarily aerobes, since the aerated water

if flowing through the gravel at a pretty good rate. There are some MFCs that uses aerobes,

such as baker's yeast, and the setup may be similar (as I recall many of them use methylene

blue as a moderator) so it may work anyway. It may be a little tricky to set up the experiment

in a way that doesn't fool you into thinking it worked, since the currents are very small even in

one that is working normally. Any bits of dissimilar metals in the electrolyte can form a battery

that overwhelms the MFC current. Copper poisoning of the microbes can also happen.

I recall one design from the 1960's that used yeast, and it used the membrane from an egg

as the proton exchange membrane. A lot cheaper than Nafion if all you want to do is demonstrate

the effect. You can leave the shell on the egg, and just put the yeast and sugar in the shell through

a hole in the top (after emptying the egg contents into your frying pan), and setting the egg in

some salt water with methylene blue in it. Add electrodes and a microwattmeter and you're in

business.

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[Patrik]

The salt bridge is cheap and easy though - no real need for Nafion for
a DIY microbial fuel cell. I believe I've also seen one that used an
unglazed clay pot as the barrier, which would make for a great 3rd
world country design, if it weren't for the fact that MFCs provide so
damn little electricity.

Ah, here you go:

Performance evaluation of low cost microbial fuel cell fabricated
using earthen pot with biotic and abiotic cathode.
http://www.ncbi.nlm.nih.gov/pubmed/19800223

Rice mill wastewater treatment in microbial fuel cells fabricated
using proton exchange membrane and earthen pot at different pH.
http://www.ncbi.nlm.nih.gov/pubmed/20615762
http://rshanthini.com/tmp/CP307/UsedRiceMill201079.PDF

> On Fri, Sep 23, 2011 at 8:44 AM, John Griessen <j...@industromatic.com>wrote:
>
>
>
>
>
>
>
> > On 09/23/2011 01:22 AM, Thomas Stowe wrote:
>
> >> Maybe you should try to develop something more conductive and possibly
> >> porous for the bacteria to live in, with or without the mud.
>
> > Might the same bacteria that set up life cycles in sand filters for ponds
> > be good for this?
>
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[dumpa]

Thanks for all the info. This would be my weekend project.

I'm going to try use my worms compost. It seems quite simple. 

I haven't found much information about what makes a good anode and a good cathode. I will experiment with what I can find.

thanks again

[Gavin McQuillan]

Dumpa,

I did some really basic experimentation with river sediment and
graphite anodes (using electrically conductive epoxy to afix it to my
lead wires, then non-conductive epoxy over that to insulate from the
water). Here's where I took my experimental design (I used freshwater
rather than saltwater). Here's a link to the paper:

http://bit.ly/tey0YR

I wasn't able to generate a measurable amount of voltage out of the
system. I didn't have any kind of current capturing set up. I might
try it out again with a salt bridge.

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[Patrik]

Hi Dumpa,

Ideal electrode material would be something that is conductive (duh),
inert (so you don't generate all sorts of chemical reactions which may
inhibit microbial growth) and with a high surface area (because it's
the bacteria contacting the electrode that generate the electricity).

In practice, that means most people use carbon cloth or graphite
electrodes. You can get a graphite rod out of a battery and use that.
Or you could even use carbon fiber cloth intended for light-weight
composites.

[Patrik]

On Oct 27, 3:28 pm, Gavin McQuillan <gavin.mcquil...@gmail.com> wrote:
> I wasn't able to generate a measurable amount of voltage out of the
> system. I didn't have any kind of current capturing set up. I might
> try it out again with a salt bridge.

With a decent volt meter, you should be able to see *some* potential
in open circuit, although it may only be in the mV range. Once you
attach a load across the MFC, the voltage can drop significantly,
especially if you have high internal resistance.

Make sure you have one aerobic and one anaerobic side. The anareobic
electrode will be the anode: microbes oxidizing carbon sources in the
sediment will donate electrons to the electrode, instead of to oxygen.
If you're just using some sediment in a jar, your layer of sediment
has to be thick enough to become anaerobic at the bottom. If the
sediment has been shaken up, or if you trapped big air pockets in the
jar, it can take a while before it's sufficiently anaerobic. Adding an
easily accessible carbon source like sugar can help use up the
remaining oxygen quickly (and any CO2 generated can help purge oxygen
as well).

[Cathal Garvey]

"Carbon Cloth" meaning high-tech carbon fiber, or charcoal'd rags?
Serious question! :)

BTW if it's relevant to anyone's project, platinum is often used on/as
the aerobic electrode to help catalyse the recombination of
electrons/H+/O2, and you can get cheap platinum (albiet barely any of
it) as costume jewellery in some department stores. They deposit a few
atoms of platinum on gaudy rings and sell them for �5-8, perfect for
science! Surface area for reaction won't be nearly as good as a
made-for-purpose cloth/mesh electrode, but it won't cost as much either.

I'm really interested to see people experimenting DIY with MFCs, thanks
for sharing your work Dumpa, Gavin. I occasionally scour the pop-sci
news and deeper literature to learn of progress on conductive pili in
G.sulferreducens etc., can't wait til that system is ironed out more
concretely so we can start experimenting from a DIYsynbio angle.

Answers I'd like include; do the pili conduct all on their own, without
special extracellular cytochromes? (Recent research suggests yes)
Do they need intracellular cytochromes to link them to the metabolic
cycle? (Probably..)
Can you get this to work in an aerotolerant anaerobe, so the presence of
oxygen is no longer limiting? (Who knows?!)

[Patrik]

On Oct 27, 11:29 pm, Cathal Garvey <cathalgar...@gmail.com> wrote:
> "Carbon Cloth" meaning high-tech carbon fiber, or charcoal'd rags?
> Serious question! :)

I meant high-tech fiber, although I do vaguely remember something
about using char cloth as an electrode as well.

Sheets of high-tech carbon fiber are expensive, but you don't need
much. If you know someone who works with carbon fiber epoxy, you can
probably get a scrap for free.

[Simon Quellen Field]

That said, you might try rubbing powdered graphite lubricant into

some cloth to see how that works. Cheaper, and hardware store accessible.

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[PatrickG]

> Can you get this to work in an aerotolerant anaerobe, so the presence of
> oxygen is no longer limiting? (Who knows?!)

Hasn't Dr. Logan at PSU occasionally used Shewanella spp., which IIRC
are at least aerotolerant, and I think can actually use O2 as a
terminal electron acceptor. Obviously under aerobic growth the MFC
wouldn't work (seems that the bacteria would much prefer to use O2 as
a terminal acceptor) but it's a good way to build up a culture rapidly.

[Cathal Garvey]

Well, that's what I mean; Can the system that couples respiration to metal function in the absence of oxygen? Is it a "choice", or does O2 hijack electrons before they can be dumped at the electrode?

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[Patrik]

If there is oxygen available (and if it doesn't kill the cells in the
first place), that is a much better electron acceptor than any
electrode. Essentially, you can think of the electrode as oxygen with
a big resistor in the way - kinda.

On Oct 28, 2:17 pm, Cathal Garvey <cathalgar...@gmail.com> wrote:
> Well, that's what I mean; Can the system that couples respiration to metal
> function in the absence of oxygen? Is it a "choice", or does O2 hijack
> electrons before they can be dumped at the electrode?
>

> On 28 October 2011 21:20, PatrickG <pgrina...@gmail.com> wrote:
>
>
>
>
>
>
>
>
>
>
>
> > > Can you get this to work in an aerotolerant anaerobe, so the presence of
> > > oxygen is no longer limiting? (Who knows?!)
>
> > Hasn't Dr. Logan at PSU occasionally used Shewanella spp., which IIRC
> > are at least aerotolerant, and I think can actually use O2 as a
> > terminal electron acceptor. Obviously under aerobic growth the MFC
> > wouldn't work (seems that the bacteria would much prefer to use O2 as
> > a terminal acceptor) but it's a good way to build up a culture rapidly.
>
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[Gavin McQuillan]

Patrik,

Granted. That's what the experimental design in the paper I linked to
makes pretty clear. In retrospect, I think I didn't have nearly enough
sediment: only about 1/2" in the bottom of a big erlenmeyer flask.
That's probably where I'd need to revisit the experiment.

I've also read studies that suggest that this form of micro habitat
will replenish these electrons (from the cathode to the anode) very
slowly through a "sulphur cycle" where sulphur ions slowly find their
way into the anaerobic realm as sediment. I don't have a citation for
it, but I'd love for anybody with more experience to comment. I'm also
not sure over what timescales this becomes important.

>
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[Patrik]

On Oct 28, 8:57 am, Simon Quellen Field <sfi...@scitoys.com> wrote:
> That said, you might try rubbing powdered graphite lubricant into
> some cloth to see how that works. Cheaper, and hardware store accessible.

Worth a try,although I'm not sure you'll be able to get the resistance
low enough this way. If someone give this a try, let us know!

I also just saw this site that sells a bunch a different conductive
fabrics:

http://www.lessemf.com/fabric.html

Any of the ones based on silver, copper or nickel may have issues with
metal toxicity, and/or loss of conductance due to oxidation over time.
They do have some fabrics based on stainless steel fibers that may be
a bit more resistant.

Their Ex-Static Conductive fabric is polyester with carbon fibers
woven into it. Not a great conductivity, but could potentially be
improved using graphite powder. The ideal fabric in their catalog
would be the Microwave Absorbing Sheet, consisting of non-woven nearly-
pure carbon fibers. Excellent conductivity (3 Ohm per square) and
price ($8.95 per linear foot), but it seems to be plastic coated, so
the actual surface conductivity may be much higher.

They offer a Fabric Sample Kit with 2x2 inch swatches of all their
fabrics for $10 ("Microwave Absorber not included in standard sampler,
so if you need these, be sure to specify"). Seems like a great
opportunity to experiment with a range of different electrode
materials...

[Tim Wilkerson]

Char cloth, can be used as an electrode:
https://www.youtube.com/watch?v=8Makaciz3Xc

[Tim Wilkerson]

This can be used for the circuitry, instead of a solar cell use an MFC:
http://www.instructables.com/id/Stealing-a-joule-thief-from-a-cheap-solar-garden-l/

On Thursday, September 22, 2011 at 7:34:24 PM UTC-4, dumpa wrote:

[Tim Wilkerson]

Also, a layer of sand will work as a ion bridge, I use about a 1 to 2 cm layer of sterilized (boiled) sand.

On Thursday, September 22, 2011 at 7:34:24 PM UTC-4, dumpa wrote: