From waste to energy: Comprehensive understanding of the thermal-chemical utilization techniques for waste tire recycling

With the increasing number of vehicles worldwide, the generation of waste tires has increased annually. Up to 2023, the annual global production of waste tires amounts to approximately 1.5 billion units. Therefore, properly disposing of waste tires has been a significant challenge worldwide. The thermal-chemical utilization techniques of waste tires can reduce environmental pollution and promote sustainable development. This paper reviews the waste tires' thermal-chemical utilization technologies of combustion, pyrolysis, and gasification. Burning waste tires generates a lot of heat, rapidly disposes waste tires, and produces greenhouse gas emissions that are approximately 40 % and 25 % lower, respectively, than coal and fuel oil combustion. The waste tires pyrolysis can produce carbon black, oil, and combustible gas, and the calorific value of the oil can be 44.20–45.09 MJ/kg. The gasification process converts waste tires into syngas rich in hydrogen, carbon monoxide, and light hydrocarbon gases, achieving a mass reduction of more than 65 % and a volume reduction of 80 %. The thermal-chemical utilization products of waste tires are mainly used in energy, the chemical industry, and environmental protection. Furthermore, the harmful substances that may be generated during the thermal-chemical treatment of waste tires, such as dioxins, furans, and heavy metals, need effective pollutant control technologies. Finally, exploring efficient catalysts and separation technologies, developing high-performance reaction equipment and systems, and exploring chemical looping gasification technology for waste tire utilization have been proposed. This paper helps to promote efficient waste tires utilization in environmental protection and sustainable energy supply.