Recycling of Tire Waste Using Pyrolysis: An Environmental Perspective

Abstract

End-of-life tires are a common and hazardous type of waste. According to estimates, over 2 billion tires are produced each year, and all of these tires will eventually be discarded as waste. Landfilling waste tires is strictly prohibited by the regulations of the European Union and the Environmental Protection Agency; they should be retreated and reused in an alternative scenario. As a waste-to-energy technology, pyrolysis can emerge as a useful technique to thermally degrade waste tires and produce useful byproducts in the form of liquid, gas, and char. The derived products can be filtered and used in further industries as biofuel substances. Pyrolytic oil has a high calorific value of 35–45 MJ/kg and can be used as an alternative to diesel to fuel specific vehicles. However, the environmental footprint of the technology has been widely neglected when using waste tires as feedstock. Made from synthetic and natural rubbers, tires contain a high amount of sulfur and styrene, which can cause toxic emissions and negatively affect the environmental sustainability of pyrolysis. This concept paper aims to elaborate the parameters of an operating rotary kiln reactor by reviewing previous life cycle assessment studies and applying the methodology to an industrial-scale pyrolysis plant in Northern Cyprus. Results found a maximum production yield of 45.6% oil at an optimal temperature of 500 °C. Influential parameters such as temperature, residence time, and heating rate are reviewed based on their overall contribution to the production yield and the environment. The outcome of this paper emphasizes the need in the literature to apply environmental analyses to industrial and commercial-scale reactors to test the sustainability of using pyrolysis as a tire waste management strategy. In addition, complex engineering concepts and tasks in waste recycling will be discussed in a broad and accessible manner, with the implications and future work discussed.