Penn State environmental engineers have shown, for the first time, that a microbial fuel cell (MFC) can generate electricity while simultaneously cleaning the wastewater that you flush down the drain or toilet.

Microbial fuel cells work through the action of bacteria which can pass electrons to an anode, the negative electrode of a fuel cell. The electrons flow from the anode through a wire, producing a current, to a cathode, the positive electrode of a fuel cell, where they combine with hydrogen ions (protons) and oxygen to form water.

No special bacteria are added. The naturally occurring bacteria in wastewater drive power production via a reaction that allows them to transport electrons from the cell surface to the anode. In addition, a reaction (oxidation) that occurs in the interior of the bacterial cell lowers the biochemical oxygen demand, cleaning the water.

The single-chambered microbial fuel cell is essentially a Plexiglass cylinder about the size of a soda bottle. It contains eight anodes, composed of graphite, that supply about 36 square inches of surface area to which the bacteria can adhere and pass electrons. The cathode is a carbon/platinum catalyst/proton exchange membrane fused to a plastic support tube. >from *Microbial Fuel Cell Cleans, Generates Electricity From Domestic Wastewater. February 23, 2004

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imago
> how do we clean our wastewater ?

"On a two-year trip to Mars, according to one estimate, a crew of six humans will generate more than six tons of solid organic waste--much of it feces. So what do you do with all that?

Right now, astronaut waste gets shipped back to Earth. But for long-term exploration, you'd want to recycle it, because it holds resources that astronauts will need. It will provide pure drinking water. It will provide fertilizer. And, with the help of a recently discovered microbe, it will also provide electricity.

Like many bacteria, this one, a member of the Geobacteraceae family, feeds on, and can decompose, organic material... under the right conditions, Geobacter microbes can both process waste and generate electricity. The "right conditions" might be found in a new type of fuel cell--a membrane microbial fuel cell. This device is currently being developed by a NASA-funded research team led by Dr. Bruce Rittmann, a professor at Northwestern University... The bacteria at the heart of the device feed on the waste, and, as part of their digestive process, they pull electrons from the waste material. Geobacter microbes, as well as a few other types, can be coaxed to deliver these electrons directly to a fuel cell electrode, which conducts them into a circuit -- a wire, for example. As they flow through the circuit, they generate electricity.

Microbial fuel cells are already being experimented with on Earth. For example, one prototype is being used at Pennsylvania State University to generate electricity as it purifies domestic wastewater.

To make this idea practical for space travel, says Rittmann, you have to have "a very efficient, very compact configuration." The fuel cell can't take up much room. To meet this requirement, Rittmann is considering a fuel cell of tightly packed fibers, each one of which will be a fuel cell all by itself...

The membrane microbial fuel cell is still in the early stages of its development." From 'Waste Not. NASA-supported researchers are working to develop a fuel cell that can extract electricity from human waste.' May 18, 2004

http://science.nasa.gov/headlines/y2004/18may_wastenot.htm?list77294

Cheaper wastewater-fueled device produces more electricity. "Penn State environmental engineers have removed and replaced one of the most expensive parts of their prototype microbial fuel cell and the device now costs two-thirds less and produces nearly six times more electricity from domestic wastewater... they can boost electricity production from about 26 milliwatts per square meter to about 146 milliwatts per square meter... The new design has moved the technology closer to our goal of 1,000 milliwatts per square meter... The Penn State team modified their original fuel cell by removing the polymeric proton exchange membrane that previously was bonded to the cathode and substituting carbon paper for the electrodes." From 'Cheaper wastewater-fueled device produces more electricity.' June 15, 2004
http://live.psu.edu/story/7177

London's Science Museum could use its toilets to help power its building and cut electricity bills.

Management at the museum believes recycling toilet waste could generate significant power from its three million visitors annually.

The museum is considering diverting the waste from its toilets to tanks.

There, the museum will get it processed and burnt as fuel or it may get it to produce power using a microbial fuel cell.

Bosses claim that the museum's three million guests a year could produce a staggering 1,530 kilowatt hours - enough power for 15,000 light bulbs.

“With free admission it would be a great way for visitors to give something back to the museum and help keep the overheads down,” museum director Jon Tucker said in a statement. “We have almost 3 million visitors each year and have huge electricity bills.”

Poo power, as the museum dubbed it, is also explored in a new energy exhibit opening in late July. http://www.sciencemuseum.org.uk/corporate_commercial/press/ShowPressRelease.asp?Show=265

http://news.google.com/news?hl=en&edition=us&ie=ISO-8859-1&newsclusterurl=http://news.bbc.co.uk/2/hi/science/nature/3895975.stm

see too "shit and civilization"
http://straddle3.net/context/03/en/2004_02_27.html