The solid residuals from the plasma gasifier (metal and glass) are recycled. The glass portion is particularly interesting, in that it can be used to manufacture higher-value products and other construction materials. The solid residuals from plasma gasification of municipal solid waste have been proven to be non-toxic; they pass the EPA's Toxicity Characteristic Leaching Procedure (TCLP). In fact, plasma technology is sometimes used specifically to render ash from incinerators and other gasification technologies non-toxic.
The obsidian-like slag (volcanic glass) can take different forms, depending on how it is cooled, and can then be used to make marketable products. The slag weighs about 20% of the original waste's weight, whereas its volume is only about 5% of the original waste's volume. No byproducts of the slag are toxic, and no ash is produced. Additionally, glass slag byproducts include filler for solid surface kitchen and bathroom counters, filler for walls, fine sand for road bedding, and as a component of other construction materials. Of particular interest is rock wool. Rock wool is twice as effective for insulation as fiberglass and non-toxic. Its light weight, buoyancy and absorbency make it a potential oil spill cleanup material.