A waste processing apparatus for processing a column of waste in a processing chamber having one or more gas outlets at an upper part thereof and one or more plasma torches an output end thereof extending into a lower part of the chamber. The apparatus is characterised in having one or more oxidising fluid distribution and mixing chambers and one or more oxidising fluid inlet associated therewith for providing oxidising fluid to said distribution and mixing chamber from a suitable source, wherein each oxidizing and mixing chamber has a peripheral opening in substantially continuous peripheral fluid communication with a column of waste accommodated in the lower part of the chamber and in fluid communication with the oxidising fluid inlets, and further, the outer peripheral wall of the distribution and mixing chamber is formed by a lateral outward displacement of an inwardly-facing wall of the lower part of the processing chamber with respect to an inwardly-facing wall of the upper part of the processing chamber. The oxidising fluid inlets are separate from and associated with the plasma torches such that during operation of apparatus oxidising fluid flowing from the oxidising fluid inlets into said distribution and mixing chamber is directed at a high temperature zone provided by the plasma torches that are associated with the oxidising fluid inlets.