The energy contained in a plasma allows gasification of low-energy fuels such as household and industrial waste without the need for an additional fuel. Thermal plasma is an excellent technology for the conversion of waste into valuable synthesis gas and a vitrified slag. The high-temperature condi­tion that exists in the plasma gasification produces a cleaner synthesis gas compared to what is achieved in the conventional gasification process. The inorganic matter (such as glass, metals, silicate, heavy metals, etc.) contained in MSW is converted into a dense, inert, no-leaching vitrified slag. The syn­thesis gas can be used for heat and electricity or it can be converted to biofu­els via Fischer-Tropsch synthesis. The vitrified slag can be used as a building material additive [65].

The synthesis gas in the plasma gasification process contains the plasma gas components. Air is often used as gas for economical reasons and for pro­viding oxygen, but other gases such as nitrogen, carbon dioxide, steam, and argon have also been tested. The literature [66, 67] has shown that the plasma torches operating with steam offer definite advantages for waste processing applications. Gasplasma™ technologies for waste treatment use electricity as the energy source and that makes the system more flexible and controllable and variable waste input does not pose problems. Thermal arc plasmas dom­inate in waste treatment because they are relatively insensitive to changes in process conditions. Inasmuch as solid waste treatment requires decontami­nation in combination with volume reduction and immobilization of inor­ganic contaminants, most plasma-based waste treatment systems make use of transferred arc reactors offering high-heat fluxes which facilitates solid melting [61].

Fundamentally, plasma technology application to waste treatment is divided into two categories, single-stage and two-stage. Here we briefly examine some specific examples of each of these categories [7].