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Welcome to the Energy & Environment (E&E) Exchange, a blog dedicated to science and engineering topics that are (generally) related to energy and the environment. This blog is meant to encourage discussion about the challenges and possibilities surrounding sustainability through science and technology. The blog's owner, cheme_wordsmithy, is a former technical writer and engineering editor at IEEE GlobalSpec, the company that powers CR4.

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Superbugs from the Sky

Posted February 29, 2012 9:10 AM by cheme_wordsmithy

Microbes, or microorganisms, are tiny "bugs" that have significance in a number of biological processes, including some very familiar ones like human digestion. In the energy realm, microbes are used in the production of methane, ethanol, and various other liquid fuels. They also are used to generate electricity through the processing of nuclear wastes, sludge, and wastewater.

But scientists have recently found usefulness in a particular species of bacteria - Bacillus stratosphericus. This microbe, as its name might suggest, is found in high concentrations in the earth's stratosphere. This sky bug has been a major player in creating a new artificial biofilm that doubles the output of a microbial fuel cell.

(<-- Credit: Tripleman)

Microbial Fuel Cells

Microbial fuel cells (MFCs) are biological fuel cells that convert chemical energy to electrical energy using microbes as the catalysts. They operate by taking advantage of the natural processes that bacteria undergo when they digest fuel or waste (animal manure, biomass, etc.) to gain energy. Specifically, fuel cells capture the electrons transferred from an electron donor (e.g. glucose, acetate) to an electron acceptor (oxygen) and use them to generate electricity.

(Microbial fuel cell diagram. Credit: Greeniacs)

MFCs are inexpensive to design compared to other types of fuel cells, and provide convenient generation of energy from waste which might otherwise be sent to a landfill or disposed through other means. The conversion process is also direct to electricity, which means much higher energy yield rates than by first converting the organic matter into a biofuel and then combusting it (no waste heat). Specifically, MFCs have operating efficiencies up to 80% with theoretical yields of 3 kWh electricity for every kg of organic matter (dry weight). This is compared to yields of 1 kWh electricity and 2 kWh heat per kg for hydrogen and biogas production - achieving overall efficiencies around 30%.

(Microbial Fuel Cell - Credit: National Science Foundation -->)

But while the electrochemical bottlenecks have decreased considerably from the growing success of catalytic fuel cells, other factors have made the MFC more of a dream than a reality. Losses from overpotential, turbulence, activation, membrane resistance, and upscaling are all problems. Additionally, power production only averages 0.5 Volts per cell, meaning an extremely large footprint is required to create sufficient amounts of power

Superbugs to the Rescue

Biofilms are surfaces which contain and aggregate microorganisms. They are the source of the bacteria (microbes) used in microbial fuel cells and are what catalyze and drive the reaction. Biofilms usually contain a mix of different types of bacteria rather than just a single kind.

(<--Credit: Open Energy Info)

B. Stratosphericus, the bug from the sky, is a particular microbe with good power-generation abilities. It was one of 75 different types of bacteria tested for its abilities. The scientists selected and mixed the best of these species to create an artificial biofilm with the most advanced properties. The result was a biofilm that nearly doubles the output of the MFC - from 105 Watts per cubic meter to 200 Watts per cubic meter.

What It Means

This breakthrough is not going to immediately solve all the problems of the MFC. Each individual cell still only produces enough juice to power a light or two, making it only truly effective for remote parts of the world without electricity.

However, the principle behind manipulating the types and concentrations of bacteria on a biofilm will open the doors to possibly even more efficient cells. After all, "there are billions of microbes out there with the potential to generate power" says Grant Burgess, Professor of Marine Biotechnology at Newcastle University.

Billions… and they only looked at 75. I guess that means there will always have more to test.

Sources:

Microbialfuelcell.org - Microbial fuel cells: performances and perspectives (pdf)

Greeniacs - Microbial Fuel Cell

Science Daily -Stratospheric Superbugs Offer New Source of Power

The Engineer - Artificial biofilm helps double output of microbial fuel cell

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Join Date: Mar 2012
Posts: 14
Good Answers: 1
#1

Re: Superbugs from the Sky

03/11/2012 4:20 AM

Here is some additional reading on these microbal species. It should be noted that those upper stratospheric and tropospheric bacteria are also found on the ground, and in water at different altitudes and locations around the world.

ijs.sgmjournals.org/content/56/7/1465.full.pdf

the scientist who did this study also admit to the fact that there is a possibility that early spacecraft and high altitude aircraft experimentation could have taken some of these bacteria into the stratosphere and troposphere on the aircraft and introduced into then at the various location that the parts were manufactured and assembled.

Microbacteria are very interesting creatures. But one thing they all have in common they are meant to destroy not build. That is there primary purpose in biology is to break down one thing and leave behind another, it waste. when a bacteria has run its course it goes dormant awaiting its next call to duty. harnessing microbs for energy may prove to be more dangerous than we care to think about.

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