Expansion of a mechano-chemical plant for remanufacturing waste tires into rubber sheet and profitable wire steel by-products: A quantitative sustainability assessment

Abstract

Existing mechano-chemical plants remanufacture waste tires into rubber sheet and recover nylon fibers and metal wires. As a novel expansion of this process to improve its profitability and sustainability, this study proposes the integration of a pyrolysis–distillation system to produce energy products and machinery to produce by-products from the waste steel, such as galvanized wire, nails, and crimped mesh. A quantitative analysis was performed to evaluate the amount of steel wire, energy, and CO₂ emissions saved by the proposed process. Furthermore, the potential profit was calculated at low and high potential scales, representing sustainable national and international development, respectively, with the aim of establishing a circular economy. Twenty-four alternatives based on technical variations were developed and their technical feasibility and potential profit were evaluated and ranked, providing valuable information for decision makers selecting plant layout options. The economic, environmental, and technical feasibility indexes were calculated and used to specify the social feasibility index. Finally, a quadrilateral-bottom-line sustainability development approach was used to calculate the final sustainability index, showing that the proposed integration is indeed a sustainable business approach. The findings of this study prove that there are significant benefits in expanding existing remanufacturing plants to extract value from the many different materials in waste tires.