Clean incinerators have been around for at least a decade[1] - potentially longer, as the Japanese have been separating out their burnable garbage from non-burnable for years.
[1] https://www.nytimes.com/2010/04/13/science/earth/13trash.htm...
[1] https://www.nytimes.com/2010/04/13/science/earth/13trash.htm...