A method for processing of plastic and/or rubber waste to generate energetic gas comprising aliphatic hydrocarbons C1-C4, carbon oxide and hydrogen, wherein the waste may comprise halogens, sulphur, nitrogen and oxygen and may be contaminated by substances of inorganic origin comprising ceramic and metallic materials, the method comprising processing the waste in a pyrolysis process, wherein a powdered waste material is fed to a microwave drum reactor (102), where it is heated by microwaves while being moved through the reactor (102), the method comprising: conducting the pyrolysis reaction inside the reactor (102) at a temperature of 800-950° C. to obtain end products comprising gases, dust and a porous char of a large surface area having absorptive properties; separating the char from the other pyrolysis products by deposition; directing a portion, preferably a quarter, of the obtained char to a filter (105); directing the dust and gases to a gas cooling apparatus (103) comprising at least two synchronized screw conveyors, wherein the gases are cooled to a temperature of 120-160° C. and wherein the dust and the condensate are directed to the filter (105) filled with the char; and feeding back the mixture of char, condensate and dust from the filter (105) to the microwave reactor (102).