InfoSciTex “Green Energy Machine” or GEM waste-to-energy conversion system, fits on the back of a truck and can shred three tons of trash per day—including paper, plastic, wood, food, and agricultural waste—and turn it into a synthetic gas mixture which can then be used to fuel electric generators or building heating systems.
In essence, it’s a mobile version of the factory-sized gasification pilot plant that Boston cleantech startup Ze-gen has built in New Bedford, MA (see my August 2007 story)—except that IST Energy uses a different kind of vessel to gasify waste, a “stratified downdraft gasifier,” in place of Ze-gen’s giant vat of molten iron. The unit takes up as much space as about three cars, and can be backed up to a building’s loading dock, or wherever its dumpsters are stowed.
The company built the Green Energy Machine in response to a request from the U.S. Army, which wants to cut down on the volume of trash, mostly from field kitchens, that it has to convoy across Iraq and Afghanistan. And IST Energy CEO and president Stu Haber says he expects the military to become one the prime customers for the machines, which will be ready for delivery this summer. But he says the GEM is also ideal for commercial and municipal facilities such as industrial plants, hospitals, universities, prisons, sports stadiums, and city waste transfer stations—”really, anybody who generates at least two tons of waste a day, which covers a huge market.” (For comparison, the town of Lincoln, MA, generates 6 tons of solid waste per day, and the Prudential Center development in downtown Boston generates 11 tons, according to Haber.)
While the machine isn’t cheap—IST will charge $850,000 per unit—its major selling point is that it can greatly reduce customers’ waste disposal and energy costs. About 95 percent of the material fed into the GEM is converted into gas, leaving an ash residue that is much cheaper to transport and takes up much less landfill space. (It also won’t emit methane and other greenhouse gases, as most landfilled materials do.) And not only does the machine power itself, but the extra gas produced can run a 120-kilowatt electrical generator or a 240-kilowatt-equivalent gas furnace. (For comparison, a typical standby home generator produces 12 kilowatts, while commercial emergency generators have outputs of 20 to 150 kilowatts.)
First there’s a shredder, which tears material poured into the GEM into confetti-sized flakes. Plastic, paper, food, wood, and agricultural waste make the ideal feedstock for the machine. The shredder can also deal with glass and metal, but since these materials can’t be gasified and just end up increasing the volume of ash residue, the company recommends sifting recyclables out of the input stream.
Then there’s a dryer, which takes out most of the moisture in the shredded flakes, and a pelletizer, which compresses them into dense little cylinders resembling rabbit food. The pellets are dropped into the aforementioned downdraft gasifier, which breaks them down under high heat into a mix of methane, carbon dioxide, carbon monoxide, hydrogen, and nitrogen. Finally, this “syngas” is sucked into a generator or microturbine to make electricity, or piped to a furnace to make heat.
