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Mud microbes power turtle-tracking sensors - 15 November 2007

Ocean sensors that feed on bacteria living in deep sea sediment are being developed by US researchers. The microbial fuel cells used to power the sensors are already helping to remotely track green turtles in the wild.

Sophisticated sensors let oceanographers study various aspects of the ocean over long periods of time, but replacing these sensors' batteries can be a complex and costly process, especially if they are positioned far out at sea and deep beneath the surface.

Oceanographers at Oregon State University, US, say a simple solution is to harness microbes in sea-floor sediment to provide a constant supply of power instead.

So they have developed fuel cells that feed on microbes – using an electrode to collect electrons released by bacteria living in the low oxygen environment. These electrons are diverted around a circuit to provide power and are then combined with oxygen and hydrogen ions to form water, balancing the electrochemical reaction.

Sewage power

Microbes used in this way are have previously been sourced in sewage, but Mark Nielsen and colleagues at Oregon State University are working on systems that use those found in ocean sediment instead. They have now begun testing prototypes in ocean environments that provide sufficient power to run simple oceanographic sensors.

"Sea floor sediment is a microbe-rich anoxic environment that can provide electrons," Nielsen told New Scientist.

The fuel cells developed so far feature an open bottomed chamber that sits over a section of sediment. This chamber becomes colonised by the same microbes living beneath the surface of the sediment. "You could say it becomes an extension of that environment," Nielsen explains. "We can use an electrode with very high surface area inside the chamber to get maximise power."

Click here to read the remainder of this article on New Scientist Environment