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Waste to Watts: Portable Refinery Transforms Trash into Power

Kitchen trash stinks, unless it can be turned into electricity, starting in Army field kitchens
plastic bottle mound



© REED KAESTNER/CORBIS
Mr. Fusion. If you're a fan of the Back to the Future" trilogy, you will recognize that as the name of the Cuisinart-like machine that converted beer and banana peels into nuclear power for the vaunted "flux capacitor" that allowed Dr. Emmett Brown to time travel. It is also the name—"whether we like it or not"—of a new, mobile refinery that turns kitchen waste into fuel and, ultimately, electricity, according to Jerry Warner, president of Defense Life Sciences, the company that has coordinated the research to build the first working prototype of such a machine for the U.S. Army.

The real "Mr. Fusion," or "tactical hybrid refinery" to use Army-speak, processes the waste produced by a typical kitchen—food, plastics, paper—into fuel that runs a standard diesel generator. Roughly the size of a van—13.3 feet long by eight feet wide and eight feet tall—the refinery can fuel 90 percent of the energy needs of a generator able to pump out 150 amps of electricity.

It works via parallel processes. The waste is first sorted—already standard practice at Army field kitchens, its first potential home—and then run through an industrial-strength shredder. The "ugly-looking gruel" that results, Warner says, separates into more liquid organic materials that funnel into a biocatalytic vat, and more solid materials—plastics—that find their way to a gasifying chamber. Inside the vat, enzymes and yeast—with a leavening of antibiotics for safety—digest the organic gruel into ethanol. Inside the gasifier, the plastic pellets turn to gas at temperatures of 600 degrees Celsius.

"As the waste material is introduced you can produce your gas from the gasifier within an hour and you'll start getting ethanol at six hours. By about 12 hours you can displace the diesel fuel to less than 10 percent," Warner notes. "It's scaled to take in about 2,500 pounds of mixed waste per 24-hour period."

Both of the resulting fuels—ethanol and gas—are then burned in a standard diesel engine to generate electricity. Of the 150 amps this generator can crank out, the refinery's internal workings only require 13 amps or so, and the only waste produced is a fine ash remaining from the gasification process that needs to be removed every 48 hours. "It just gets evacuated in the same process as the waste would have," says Warner, a former infantryman. "Except now you have one thirtieth of the problem."

The prototype at Purdue University cost $950,000 to build, most of which came from the Army. More tests and demonstrations are in the waste refinery's future and the engineers are optimistic that it may be capable of achieving even greater efficiency—reducing diesel requirements to as low as one or two percent of the fuel mix. "There's a lot more energy in there," Warner says. "[Plastic] is just solidified petroleum."

Defense Life Sciences and its partners hope to have "Mr. Fusion," under another, more sober name, available for purchase within a year at roughly one third the cost of the prototype. And they are looking beyond military applications. "You might go into a large skyscraper and allow them to manage their solid waste stream right there in the building," Warner adds. "You'd eliminate the generator and hook it up to a boiler, providing a portion of the building's hot water and heating needs." The future of waste certainly seems to be power.

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