The development of waste treatment technologies for various types of waste from different sectors is inevitable. The processes should be economical and protect the environment. Synthetic polymeric materials are one of the major portions of wastes in the developed and developing countries. Feedstock recycling process appears to be most promising among the various other methods. Dehalogenation process is a key technology in feedstock recycling mixed halogenated waste plastics. In this study, two different approaches have been made to clarify the effectiveness of our proposed catalytic dehalogenation process using various iron oxides and calcium carbonate as catalyst/sorbent. The first approach (two step process) is (i) thermal decomposition of waste plastics into oil, which contains various halogenated compounds and (ii) develop dehalogenation catalysts for the catalytic dehydrochlorination of orgnic chlorine compounds from mixed plasticderived oil in a fixed bed flow type reactor. The second approach (single step process) is the simultaneous degradation and dehalogenation of chlorinated (PVC) and brominated (brominated flame retardant containing plastic HIPS-Br) mixed plastics to produce halogen free liquid products. We report a catalytic process for the dehalogenation of chlorinated and brominated organic compounds formed in the pyrolysis of PVC and brominated flame retardant (HIPS-Br) mixed waste plastics (PE, PP, and PS) derived oil. During dehydrohalogenation, the iron and calcium based catalysts were transformed into their corresponding halides, which also showed high activity for the dehydrohaloge nation of the organic halogenated compounds. The developed iron oxide and calcium carbonate carbon composites were effectively removed the halogen content with bifunctional (catalytic/sorptive) activities. The halogen free plastic derived oil (PDO) can be used as a fuel oil or feedstock in refinery. On the similar grounds, the waste polymeric materials from automobile shredder residue (ASR) were found to increase with time. The present study also focused on the development of viable technology for the feedstock recycling of waste plastics from automobile shredder residue, comparison of their liquid products with conventional liquid fuels and utilization of pyrolysis products in various applications.