Comparative life cycle assessment of reprocessed plastics and commercial polymer modified asphalts

Abstract

The use of waste plastics in asphalt mixtures as binder modifiers is an alternative to commercial polymers, which can contribute to solving problems related to waste management. It is anticipated that using reprocessed plastics in pavement construction decreases environmental impacts associated with the production of asphalt mixtures. The present study compares the environmental benefits and burdens of the application of reprocessed plastics (RPs) in asphalt mixtures in the dry process compared with those of commercial polymers. All processes for the production of plastic pellets from waste plastics, including the collection, sorting and reprocessing of waste materials, are considered, and the contribution of each stage to total impacts is identified. The results of cradle-to-gate life cycle assessment of a declared unit of one tonne of asphalt manufactured with RPs are compared with commercial polymers and conventional asphalt mixtures. The results show that, although the utilization of RPs increases the environmental burden of the manufacture of asphalt mixtures, it offers an environmentally friendly alternative to commercial polymers. Moreover, the high contribution of the collection stage to the resource damage category of RP pellet production highlights the importance of waste collection management in order to minimize the consumption of resources and associated impacts. Although the environmental benefits of RP modified asphalts decrease with increasing mixing temperature, these mixtures are environmentally superior to competing alternatives at lower temperatures and the optimum bitumen content of 5.3%. However, the emission of toxic fumes when temperature increases are subject to further assessment.