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1 June 2002

Sewage as base of power

Warwick, England—Is it possible to convert wet waste from sewage farms and paper mills into a source of power? Researchers at the University of Warwick's Warwick Process Technology Group say, "Affirmative."

Dr. Ashok Bhattacharya's team figured out how to extract very pure levels of hydrogen from wet biomatter, such as sewage or paper mill waste. This very pure hydrogen then works as "fuel cells" to power homes, factories, and cars. The research team will build these "plated membrane reactors" as small industrial units, no bigger than a large room in some cases. They will add them directly to the sites of sewage plants or paper mills.

Previous attempts to extract pure hydrogen from biomatter to power fuel cells met with only limited success, even with dry material. The new process extracts very pure hydrogen from the difficult but abundant wet biomatter and even allows the material's water to generate more pure hydrogen.

First researchers gasify the waste biomass, breaking it down into its methane CH4, water H2O, carbon monoxide CO, and carbon dioxide CO2, and some hydrogen. All these gases then feed into a reactor, which uses them in a chemical reaction and then extracts the hydrogen.

Normally, this reaction would reach equilibrium and stop once it has generated a certain amount of hydrogen. But the research team uses a palladium-coated, ceramic, semipermeable membrane as part of the reactor that lets only hydrogen through. This allows them to harvest very pure hydrogen from the system and keep the reaction going as long as it is fed with the waste biomass because the hydrogen never builds up to the point where it reaches a chemical equilibrium.