A review on harnessing the energy potential of pyrolysis gas from scrap tires: Challenges and opportunities for sustainable energy recovery

Scrap tires pose a significant challenge as a common and inconvenient form of waste, resulting in non-functional waste products that are difficult to dispose of effectively. With an annual production of nearly 1.5 billion tires, the environmental pollution caused by their eventual disposal in the trash stream is a pressing concern. The European Union has imposed a ban on tire dumping, emphasizing the need for tire collection and recycling instead. Pyrolysis emerges as a promising solution, enabling the dissolution of waste while simultaneously yielding valuable by-products. This process involves the transformation of tires into gas, liquid, and solid phases. The heat value of pyrolytic gases during liquefaction reaches approximately 30–40 MJ/Nm3, providing ample energy not only for sustaining the pyrolysis process but also for alternative applications. Nonetheless, the presence of excessive SO2 in flue gases poses a significant obstacle, surpassing legal limits, while HCl, NOX, and heavy metals may also contribute to similar environmental concerns. To meet regulatory standards and optimize pyrolysis efficiency, gas cleaning techniques are indispensable for eliminating these chemicals from the dissipating gases generated during discarded tire pyrolysis. Given that pyrolysis gas exhibits excellent potential as a gaseous fuel, this article's primary objective is to comprehensively evaluate its characteristics for energy recovery, while also outlining potential consequences that need to be addressed.