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New Anode and Cathode More Than Double Output from Microbial Fuel Cells

25 March 2007

Bb_fuelcell
A brush anode and a tube cathode next to an assembled MFC containing one anode and two cathodes. Click to enlarge. Source: Yi Zuo, PSU

Researchers at Penn State have developed a new graphite brush anode, consisting of graphite fibers wound around a conductive, but noncorrosive metal core, for use in a microbial fuel cell (MFC).

Use of the new anode more than doubles the power output of fuel cells using earlier generations of electrodes. A new membrane-tube air cathode, adapted from existing wastewater treatment equipment, completes the circuit.

When anaerobic bacteria are placed in the oxygen-free anode chamber of an MFC, they attach to the electrode. Because they do not have oxygen, they must transfer the electrons that they obtain from consumption (oxidation) of their food somewhere else than to oxygen, and so they transfer them to the electrode. The two electrodes of the fuel cell are at different potentials, creating a bio-battery (if the system is not refilled) or a fuel cell (if refilled).

In the process, the bacteria consume organic matter in the wastewater and clean the water. The Penn State approach uses the bacteria that naturally occur in wastewater, requiring no special bacterial strains or unusual environmental demands.

Previously, Logan and his team showed that small, rectangular fuel cells that used a carbon fiber paper as anode and a carbon fiber paper with platinum catalyst as cathode could produce electricity and clean water from wastewater. However, commercial scale-up for carbon fiber paper cells was not practical.

Using brush anodes, which have 300 to 1,500 times more surface area than the previously used carbon paper anode, the fuel cells created more than twice the power produced by the fuel cells two years ago. A fuel cell using a small brush about 1 inch in diameter and 1 inch long produced the equivalent of 2.4 watts for every 260 gallons of water using the carbon paper cathode.

Other carbon anodes were problematic because the pores or spaces became clogged with the biofilm and lost efficiency, but because the brush contains very fine fibers with plenty of circulation room around them, dead bacteria do not clog the brush.

The carbon fiber brushes are electrically conducting, very inexpensive to produce and supply large surface area for the bacterial biofilm attachment. These anodes can be made by any existing brush manufacturer in any size or shape desired. The anode is no longer a limiting factor in power production for these cells.

—Bruce E. Logan, the Kappe Professor of Environmental Engineering

For the cathode, the researchers looked for a new type that could produce much more surface area. The cathode must have one side exposed to the oxygen to work. The researchers looked at membrane tubes currently used in wastewater treatment applications. Commercially available in a variety of sizes ranging up to 6 to 8 foot tall, these membrane tubes are not electrically conductive.

The team painted the membrane tubes with conducting graphite paint and added a cobalt-based catalyst. The painted tubes did work to produce power, but not as much as the carbon paper doped with platinum.

The researchers tested two cathode configurations, one with the catalyst on the outside of the tubes and one with the catalyst on the inside of the tube. In the best test case, the researchers used a carbon fiber brush anode and two tubular cathodes of about .6 inches in diameter doped with a cobalt catalyst on the inside to produce 18 watts per 260 gallons of water and achieve a charge efficiency of more than 70%.

The newly configured anodes and cathodes also allow for a variety of configurations of the fuel cell.

We showed a proof of concept with these tubes, but now we have to improve the efficiency and reduce costs. With these new anodes and cathodes the design of a wastewater treatment reactor could be as simple as a large tank with the brushes and tubular cathodes inserted into the same tank

—Bruce Logan

The results are reported in a pair of papers in Environmental Science and Technology.

The National Science Foundation and the US Department of Agriculture supported this work.

Logan’s team has also explored the use of microbial fuel cells to convert corn stover directly into electricity following the pre-treatment of the biomass to release the sugars. (Earlier post.)

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Comments

Oh No, poop mobiles!

Im a little confused , is it a waste treatment system or will it run a car ?
either way these guys are really scraping the bottom of the barrel!

As a mechanic (with other interests)I am very aware of the necessity of closing the loop in the ICE. This is not just about diagnosis but a practice relating to how buisness is done so it is a principle an
Ethical principle
so if you dont understand that then you wont see how this type of technology is critical to restoring our environment to health. That it's pedigree comes from sewage is a huge bonus. I see a great need to close that loop. No more ocean outfalls, pollution to rivers\ drinking water resouces etc. We think in language sos \fish think in water\ resouces etc.
As our ways of doing the buisness leave the dark ages, we should be able to recycle this sum total of human endevor.
Good work guys.
A Doctor friend sails around the world but coming into port, dials ahead to his coleagues to resupply with liposuction.
The bioD was attracting too many seaguls -couldnt see where he is going.

Arnold:

HUH???

Oh no should have waited till morning but I thank you for your honest criticism.
There is a whole body of supported theory in the area of algae as biomass. My first introduction to the concept of algae agricultyre was through some of the numerous books on Permaculture : ( defined as PERMAMENT AGRICULTURE ) by the modern day founder Bill Mollison through the 1970's 1980's.
He would be the first to explain that the concepts and practice draw on history for inspiration.
The many benifits attributed to Algae Pond Farming include the furthering of the first law of sustainable living:
DO NO HARM.
We who farm the land in this hard place have a proud tradition of inovation in technology driven by the geo specific factors including distance , poor soils compared to those that our forebears had adapted to in Europe and indeed anywhere else in the world or even over the other side of the hill.
Our explorers took notice of the local knowledge or
so often perished.
The more we trusted them the more they took with them, often the less prepared they were to understand what had the thousands of years of refinement represented in the people they were not prepared to acnkowledge.
Draw From Nature:
She's been 'at it' long enough to see the numbers resolve. She doesnt waste time looking for short ter solutions she wastes nothing adapts everything and resolves as many issues as can be handled in as few actions as possible, that is economises her efforts as evolution has to prioritize finite time. Adapting in a timely fashion or face extinction of that line.
History is our best teacher:
We learn from our mistakes and those who dont are destined to repeat them (thats acceptable UNTILL THE CONSEQUENCES ARE OVERWHELMING) then a more considered approach is the way.
Algae from sewage, phytomining, water remediation, fertilizer production, high protein animal fodder,
fish farms, aquaculture, carbon sequestration through Bio recycling,
Education in biological sciences possible in the attatched laboratory that would be necessary to monitor the developed systems,
Waste heat from many varied Industrial processes help provide an optimised stable environment to cultivate the various organisms alae fungi, bacterium, animals from fish to fowl harnessed to the cause,.
Our population centers all have reticulated water and sewage infrastructures in place many areas of the world would be well served by this simple improvement to health. So lets say the difficult part of this technology is ALREADY in PLACE. That wich isn't SHOULD BE : (sewage ponds) labs, education, vision, responsibility, etc .
The Cost so Far : Nothing more than what we should have been doing for too long. Nothing compared to the cost borne by the critters we share this planet home with.
How much will it cost? click here to go to the top of the page if that doesnt work 'dont bother'.
arnold

in other words, what the 'techies' will ever admit is that the solution is to consume less...much less...
on the other hand, pc is new hype, has been around for 4,000 years at least in indonesia, brazil, africa, elsewhere, see bm's intro in his book, also done in ca much earlier than bm's by ca's architect general svdr under jb

Hey Joe,
Been wondering about the blue lighted name ot the end of comments in Greencarcongress.
Now I know.
I guess you can see I'm quite passionate about this matter of smarting our way out of the pickle we are in. I see decades of good advice from thoutfull persons p'd against the wall and forgotten. Or not followed through with the neccessary determination Now we may have determination in spades but are the best options being canvassed.
As a farmer I can't contemplate action that would addreess only one or two issues at a time but when a solution presents offering solutions to three four or five issues, I find It very hard to sit on hands and see opportunity fly out the window .
In your letter you mentioned bm's book ? I am familiar with Buckmeister ? Fuller and have heard of some of his marvelous ideas but confess never to have been able to obtain copy or read any as the relevent ones seem unobtainable or out of print. (More p'd against the wall.) If had to prioritize, which order would you suggest reading.
I hav'nt got ca's (california?) general svdr under jb ? HELP!

regs anold.

It is interesting when i realized that this tech could probably turn a wastewater treatment plant into a giant yet highly efficient MFC after improved commercial scale-up. And i prefer to believe that the barrel is actually with no bottom, while the feeling of scraping one can usually help do a better job.

Want to purchase components and materials needed to run a device!most important anode,cathode please send info! craftecwelding1@att.blackberry.net

Want to purchase components and materials needed to run a device!most important anode,cathode please send info! craftecwelding1@att.blackberry.net

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