The experiments simulating events taking place during multizone combustion of fibrous deinking byproduct generated in pulp and paper mill were conducted. The multizone heating consisted of the low-temperature region (< 1000°C), followed by the high-temperature zone (1500°C), and a second low-temperature region (« 1000°C) proceeded by sudden quenching. The simulation of such Low-High-Low temperature process (LHL) was conducted in a high-temperature Cahn TG-171 thermogravimetric furnace coupled with a Mattson Galaxy 5020 Fourier transform infrared spectrometer. Morphological changes of the fibrous byproduct, from a mixture of fibers through sintered particles formed between 1100 and 1400°C and molten ash particles observed above 1400°C, caused encapsulation and immobilization of heavy metals (Cd, Cu, Pb) within the ash. It was also found that the temperature-time history and CH:OH ratio are important physical/chemical parameters affecting the polycyclic aromatic compounds (PACs) formation. The PACs destruction occurred during the LHL process before PACs were emitted into the atmosphere. It seems that the multizone burning may be an attractive way for the clean and efficient disposal of contaminated industrial byproducts.