e novel design does not require unstable intermediaries to shuttle electrons and thus holds promise for producing energy from sugar-containing waste materials.

Swades K. Chaudhuri and Derek R. Lovley of the University of Massachusetts used Rhodoferax ferrireducens, a bacterium first isolated from sediments collected from an aquifer in Virginia, for their bacterial battery. When the researchers exposed R. ferrireducens to a solution of glucose in a chamber containing a graphite electrode they found that when the bacterium fed on the sugar, it transferred electrons directly to the electrode, producing a current. In addition, the sugar-fed R. ferrireducens continued to grow, resulting in stable, long-term power production. The scientists also tested the bacterium's ability to convert other sugars, including fructose, sucrose and xylose (present in wood and straw), and found it to be equally efficient.

The new findings should help scientists harness the abundant energy currently stored in waste from agricultural, municipal and industrial sources. The prototype fuel cells have such desirable features as the ability to recharge and minimum loss of energy while idling. Perhaps one day electronics will be sold with the caveat "bacteria not included." --Sarah Graham

---------------

RELATED LINKS:

Ask the Experts: How do rechargeable batteries work?

Rechargeable "Green" Battery

Carbon Nanotubes Could Lengthen Battery Life

New Process Could Harness Hydrogen Fuel from Plants

From: http://www.sciam.com/article.cfm?articleID=000A0FCC-E85C-1C63-B882809EC588ED9F

News

October 12, 2000

Rechargeable "Green" Battery

Israeli chemists have come up with the first rechargeable battery made from magnesium--a less expensive, more environmentally friendly and safer metal than those used in current systems. Better yet, the researchers expect that the magnesium battery's energy density could be made considerably higher than what is possible in common lead-acid and nickel-cadmium batteries. They describe their invention in today's issue of Nature.

The new battery from Doron Aurbach and his colleagues at Bar-Ilan University follows the same basic blueprint for any battery--including an anode, cathode and conducting electrolyte. The anode is made from magnesium, as is the case in some existing, one-lifemilitary batteries. But the other two elements represent the advance. Because of magnesium's particular chemistry, most electrolytes ruin the anode's surface, but Aurbach and his team use solutions based on magnesium organohaloaluminate salts that don't create the same surface films. And the cathode is made from MgxMo3S4 (where x is a number between zero and one), which unlike most other cathode materials can reversibly bind to the magnesium ions created when the anode reacts. It is this reversal that makes the battery system rechargeable.

In fact, the new battery can be recharged more than 2,000 times and produces up to 1.3 volts—an amount that the team hopes to pump up to 1.7 volts with further refinements. Aurbach predicts that the battery will be commercially available within a year, serving first as ameans to supply uninterrupted power to computer networks during outages. --Kristin Leutwyler

--------------------------------------------------------------------------------