Recycling the Energy of Waste

Every resource carried onto a manned spaceship is precious, because it costs hundreds of dollars to lift each pound of material past Earth's surly bonds. Now that NASA is in the process of planning a trip to Mars that might take up to two years, no type of recycling can be overlooked. One thing that can provide three basic raw materials (water, energy, and fertilizer) needed for a long space journey: human waste.

By | June 21, 2004

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Every resource carried onto a manned spaceship is precious, because it costs hundreds of dollars to lift each pound of material past Earth's surly bonds. Now that NASA is in the process of planning a trip to Mars that might take up to two years, no type of recycling can be overlooked. One thing that can provide three basic raw materials (water, energy, and fertilizer) needed for a long space journey: human waste.

Most methods of recycling organic waste involve the production of methane, a flammable gas that can easily turn a closed spaceship into a roman candle. That's why NASA awarded a $100,000 (US) grant to Bruce Rittmann, an environmental engineer at Northwestern University, Evanston, to build a microbial fuel cell that generates electricity from sewage.

Such fuel cells function like a conventional fuel cell, except that individual bacterial cells split electrons from a food source and transfer them to a metal anode. The electron stream turns into electricity when it comes into contact with a cathode.

In Rittmann's model, the microbe used is Geobacter metallireducens, an extremophile first discovered in the Potomac River in 1987. He hopes to have a working prototype no bigger than a test tube one year from now. He also hopes to better understand the basic biology of these bacteria. "Right now we know what they are doing, but we don't know how they're doing it," he says. "That's what we want to find out."

- Sam Jaffe

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