Environmental life cycle assessment of the incorporation of recycled high-density polyethylene to polyethylene pipe grade resins

Abstract

Plastic recycling involves a range of potential environmental benefits, from curbing landfill and incineration rates to the reduction of greenhouse gas emissions. However, the main challenge is to find applications where recycled plastic can successfully provide the same functionality as the replaced virgin plastic. Particularly, the incorporation of recycled high-density polyethylene (HDPE) to polyethylene (PE) pipe grade resins is a great challenge that is not currently being implemented in the manufacture of pressure pipes. In this study, life cycle assessment (LCA) is applied to quantitatively evaluate the potential environmental impacts from producing PE pipe grade resins from recycled HDPE blended with virgin HDPE. The LCA involves four HDPE waste feedstocks (crates/caps, packaging/detergency bottles, post-consumer industrial containers, and automobile fuel tanks) and two PE pipe grades (PE80 and PE100). Moreover, different allocation approaches that affect the LCA of plastic recycling, namely the cut-off approach and the Circular Footprint Formula, were investigated. The recycled content was found to largely determine the LCA results. In this regard, the production of PE80 quality from the pure HDPE waste feedstocks (such as automobile fuel tanks and post-consumer industrial containers) allows a higher recycled content, thus resulting in lower impacts. Compared with a 100 % virgin resin, these two sce- narios show 80 % and 53 % less carbon footprint if the waste feedstock is considered burdens free (cut-off allocation). These percentages however decrease to 32 % and 20 % if the impacts and benefits are shared ac- cording to the Circular Footprint Formula. These trends were similarly observed for most of the impact categories evaluated, such as, acidification and fossil resources. The robustness of these results is supported by error propagation via Monte Carlo simulation.