Trash in, energy out. Sounds too good to be true, and it may yet be. But StarTech claims to have a method of rendering any waste stream into two by-products, a glass-like slag and "syngas," and a combination of mostly hydrogen and carbon dioxide, which could be used to provide hydrogen fuel for vehicles. Most impressive, Startech claims that the process would be self-sustainging. "[O]nce the cycle is under way, the 2,200°F syngas is fed into a cooling system, generating steam that drives turbines to produce electricity. About two thirds of the power is siphoned off to run the converter; the rest can be used on-site for heating or electricity, or sold back to the utility grid."In addition to the benefits of energy generation, the process also greatly reduces the volume of waste. The slag output may turn out to be usable for paving or may simply be landfilled, but requiring a much smaller volume than a comparable amount of unprocessed trash. Even more environmentally beneficial, though, are the extreme temperatures (30,000 degrees Fahrenheit, three times hotter than the surface of the sun) which break down any kind of toxic materials which are put into the system into their component atoms. In fact, the company's first units sold are in use in toxics disposal. "In 1997 the U.S. Army became Startech’s inaugural customer, buying a converter to dispose of chemical weapons at the Aberdeen Proving Ground in Maryland. A second reactor went to Japan for processing polychlorinated biphenyls, or PCBs, an industrial coolant and lubricant banned in the U.S since 1977 ("really nasty stuff," Longo says)."
There are concerns about this system. One critic noted that the slag produced from the Plasma Converter contains toxic heavy metals. However, those metals are not introduced by the process, and are present in unprocessed trash waste, as well.
Conceivably, elements that are water soluble could be leached out via additional post-processing and potentially even reclaimed and usefully recycled. However, even without these mitigations, it is easier to contain and monitor the final output in order to minimize adverse environmental effects.
Now, this is not a piece of household technology. "A Startech machine that costs roughly $250 million can handle 2,000 tons of waste daily, approximately what a city of a million people amasses in that time span." But, as the Popular Science article points out, a city with an average tipping fee for waste disposal in a conventional landfill would pay back its investment in a Startech system in about 10 years, and that's not even factoring in the excess electrical production or the sale of syngas fuel.