Garbage Truck 2.0

Nathan Mosier tweaks the "tactical biorefinery"--which eats trash and makes fuel. Credit: Purdue Agricultural Communication photo/Tom Campbell

Thursday, March 1st, 2007--

Part refinery, part generator, a new portable machine eats trash and makes fuel. Designed to convert waste from an army "field kitchen"—the refinery can handle food and packaging material. First, any organic food scraps are broken down by yeast, which produces ethanol as a byproduct. This process is called fermentation.

The leftover trash—papers, plastics, cardboards and Styrofoam—are then compressed. “They’re sort of like pet food pellets,” says Nathan Mosier, a professor at Purdue University in Indiana, who helped design the refinery. The kibbles are sent to the “gasifier,” which cooks the trash pellets under low oxygen conditions, producing methane and propane gas. These gases, and the ethanol from the fermenting station, are burned to generate electricity.

In a test run, the refinery put out 90 percent more energy than it consumed, producing as much as 55kW of power at a time —about as much energy needed to power three homes, says Mosier. Although it is generating much more energy than it needs, it still requires some diesel fuel to operate. “We would like to get that down to a much lower usage and there is no reason at all that the system can’t be converted to using biodiesel as well.”

Dubbed the “tactical biorefinery” by its inventors from Purdue, Defense Life Sciences, LLC, Community Power Corporation (CPC), Bowen Engineering, and Huston Electric, the machine is designed primarily for military applications. For a unit deployed in a remote area, the refinery not only provides free power, but it also churns tons of garbage into a garbage-bag-size amount of trash—a 30 to 1 volume reduction. The leftover waste must be emptied from the gasifier every few days.

With this kind of efficiency, should we expect to soon be fueling our cars at landfills? No, Mosier says. “You could imagine hospitals or university dorms, or other places where there are concentrations of people and waste like this. They could then generate fuel, hot water or other useful products.”

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--Flora Lichtman