Environmental assessment of rubber recycling through an innovative thermo-mechanical devulcanization process using a co-rotating twin-screw extruder

Under the umbrella of the transition toward a circular economy, the evaluation of the environmental sustainability of processes aiming to the recycling of materials is essential. Rubbers, like ethylene-propylene diene monomer (EPDM), represent a class of materials that have become an environmental, social and economic issue, so the evaluation of the end-of-life management of these materials is of primary relevance. This study investigates the environmental burdens associated with a thermo-mechanical devulcanization process for recycling of EPDM wastes by co-rotating twin-screw extruders. The Life Cycle Assessment methodology was used to carry out the analysis and eight environmental impact categories have been evaluated: Climate change, Ozone depletion, Photochemical ozone formation, Acidification, Eutrophication (freshwater), Ecotoxicity (freshwater), Resource use (fossils) and Resource use (minerals and metals). In the first step, the analysis focused on the identification and quantification of main environmental hotspots of the process. Then, the study was extended by including two comparative analyses, to better understand the magnitude of the environmental burdens generated by the devulcanization process. The results of the hotspots analysis showed that the main contribution to the environmental impacts of the devulcanization process is due to energy consumption. However, the comparison underlines how the devulcanization process for recycling of EPDM waste allows to reduce the environmental burden associated with the life cycle of rubber products.