Abstract: Waste, preferably in a pre-dried state, is passed through a carbonizing oven chamber, from the top towards the bottom and is carbonized therein through interaction with a counter flow of heated gas; that gas together with carbonization gas is taken from the chamber and pre-cleaned (to remove condensates); a portion of the pre-cleaned gas is heated and used as carbonization producing and sustaining gas; the remainder of the pre-cleaned gas is washed and used otherwise, for example, as combustion fuel in a heater for the pre-cleaned gas that will then be used as carbonizing agent. The carbonizing oven chamber can be of various construction such as a pit furnace or a revolving oven. Preferred is to commence carbonization of waste in the chamber through a thermo shock.