Incineration destroys most dangerous components of medical and other hazardous wastes, but even the hottest furnaces still produce nitrogen oxides, dioxins, and toxic ash. After years of industry efforts to develop a versatile noncombustion thermal alternative-one so hot that wastes are transformed into less harmful or even useful gases and glassy solids-a dual-heating system is proving commercially viable.
Developed by Integrated Environmental Technologies of Richland, WA, which is commercializing technology developed partly at MIT, the system recently hit a key milestone. Industrial-gas giant Praxair last fall decided to market the technology to the chemical industry to destroy toxic waste, and in the process create hydrogen. “It effectively eliminates off-site transfer and disposal, typically by incineration, of hazardous wastes,” says Gary Storms, commercial-development manager for Praxair in Danbury, CT.
The system combines two tightly controlled heating methods inside a cauldron. In the first, plasma generated by two or more graphite electrodes courses through a stream of incoming waste; in the second, waste is melted through electrical-resistive heating. The combined effect pushes temperatures to 10,000 C and creates a lavalike soup that gives off gases like hydrogen and carbon monoxide and eventually cools into chunks. Jeffrey Surma, president and CEO of Integrated Environmental Technologies, says the approach “has the ability to tune exactly where we want the input energy to go,” helping the system work for differing mixtures of waste. Nick Soelberg, a chemical engineer at the Idaho National Engineering and Environmental Laboratory, calls it “a reasonable alternative to incineration.” Other companies including Startech Environmental of Wilton, CT, are also commercializing plasma systems; eventually, perhaps, the incineration era will burn out.