There are lots of downsides...Google “msw gasification failures” and you’ll get a clearer picture. It is technically very difficult to gasify MSW and do it reliable and at large scale. There is a lot of public concern over dioxins, furans, heavy metals, and contaminated liquid waste streams. The “fuel” is incredibly corrosive and highly variable in character and quality making it hard to use.
Plasma arc trash reduction is not mere incineration of waste, nor even the typical “gasification” process, by which the waste stream is heated to about 1,000 degrees and is essentially turned into a form of carbon coke. That method would evolve a LOT of volatiles, which would have to be captured and contained some way, and the slag from this “coking” process would leave a lot of heavy metals.
The plasma arc works from a different principle, in that the trash stream is not heated to some rather low temperature of perhaps a couple thousand degrees, it is HOT, as noted, some 33,000 degrees F. At this temperature the atoms all become plasma, there is NO organic or even most inorganic substances that will retain any of their former characteristics after going through that lake of fire.
Silica, one of the most abundant of materials in the earth’s crust, would be the first to condense, fall and form the slag at the bottom, and most metal and metallic ions would be carried with it, if not immediately, then whenever the gaseous form condenses as a solid again. There is no liquid water, or even steam, at that temperature, as the water is split into free oxygen and free hydrogen, and the oxygen combines immediately with any available carbon. The most stable form of carbon and oxygen at temperatures of 2,300 degrees F. is as carbon monoxide, carbon dioxide does not form as a stable compound until the temperature falls below about 1,000 degrees F. There would be no contaminated liquid stream, without the liquid water. Dioxins and furans would also not exist at that temperature.
http://www.popsci.com/scitech/article/2007-03/prophet-garbage