Valorisation of Waste Tyre via Pyrolysis: Advances and Perspectives

Abstract

This paper first reviews the serious environmental concerns and waste management due to the rapid increase in the vast quantity of waste tyre globally. It then articulates the importance of pyrolysis as an attractive technical route for valorising waste tyre. A systematic summarisation on pyrolysis reaction chemistry is presented, including those for both waste tyre and its individual components. The key factors, including feedstock properties, reactor configurations, and reaction conditions that influence the properties and distribution of pyrolysis products and transformation and fate of impurities, are discussed. Such knowledge is essential to selecting operating parameters for optimal pyrolysis products and process performance. Potential applications of waste tyre pyrolysis products (i.e., char, oil, and gas) are subsequently surveyed and summarised. The important roles of key impurities (especially sulfur) and their derivatives, which are major constraints for commercialisation of waste tyre pyrolysis technologies, are also discussed. Remediation strategies of these impurities in pyrolysis products are summarised, compared, and benchmarked. The recent progress in process development, techno-economic analysis, and life cycle analysis of waste tyre pyrolysis processes is also covered. In closing, the remaining challenges and research gaps in the field of waste tyre pyrolysis are identified and future research perspectives are outlined.

Review and Perspectives of End-of-Life Tires Applications for Fuel and Products

“…ELT as fuel or products are associated with high emissions of toxic substances such as polycyclic aromatic hydrocarbons and volatile organic compounds. 41 A considerably more economical and environmentally benign destination for ELT is in construction materials such as pavement. However, pretreatment is usually required to improve the compatibility of ELT with the surrounding matrix (i.e., the asphalt mixture).…”

“…30 Regarding profit margin, using rubber as waste material in asphalt pavement is more advantageous than material recovery. 41 A pyrolysis plant of medium size, capable of recycling 30−40 tons per day, generates $222 per ton. However, the recycling process costs $200 per ton, leaving only a profit of $22 per ton from material recycling.…”

“…In contrast to the other routes, the construction route causes no significant environmental impact beyond emitting negligible traces of dust into the air during ELT grinding. , This route also leads to significant carbon sequestration of about 838 kg of every ton of waste tire . Regarding profit margin, using rubber as waste material in asphalt pavement is more advantageous than material recovery . A pyrolysis plant of medium size, capable of recycling 30–40 tons per day, generates $222 per ton.…”

“…ELT management routes. Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

“…The rest ends up in landfills. 40 Figure 3 compares the environmental and economic hierarchy of these management routes, 41 and Figure 4 compares the emission of primary pollutants such as CO 2 , CO, NO x , SO x , and particulate matter (PM) associated with them. Fuel production via pyrolysis leads to 54.5 kg of CO 2 per ton of waste tire used, an emission mounting to 220 kg via incineration.…”