Closed-loop recycling of End-of-Life tires via devulcanized rubber: Life Cycle Assessment and circularity evaluation with durability trade-offs

More than 3 million tons of End-of-Life Tires (ELTs) are generated annually in Europe, with 91–95% currently managed through down-cycling processes for energy or material recovery. An Italian consortium has recently developed a closed-loop recycling process that enables the use of ELTs for producing new heavy-transportation tires. The baseline formulation has been validated through large-scale road testing, demonstrating performance comparable to traditional tires. This study evaluates the environmental performance and circularity of tread compounds incorporating devulcanized elastomer obtained from ELTs. Using Life Cycle Assessment (LCA) and the Material Circularity Indicator (MCI), four formulations were assessed: a traditional virgin compound and three containing 20%, 30%, and 50% recycled elastomer (20R–80V, 30R–70V, and 50R–50V, respectively, where R and V indicate recycled and virgin rubber content). The LCA results show that natural rubber is the main contributor to the environmental impacts, accounting for more than half of the burdens in most categories. Partial substitution with devulcanized elastomer leads to consistent impact reductions, with global warming potential decreasing by 13% in the validated 20R–80V formulation. Higher recycled-content formulations offer greater potential benefits; however, sensitivity analysis highlights that these benefits strongly depend on durability. Reductions in performance can significantly offset the environmental gains, indicating that durability represents a critical threshold parameter. The circularity assessment further confirms the advantages of both material substitution and recycling pathways: the MCI increases from 0.46 for a virgin tread sent to energy recovery, to 0.73 when recycled, and up to 0.79 when devulcanized elastomer is incorporated. Overall, devulcanized elastomer can effectively improve both environmental performance and circularity, provided that adequate durability is maintained.