Assessing the circularity of post-consumer HDPE milk bottles through open-loop recycling and their environmental impact

Abstract

Plastics are key in the packaging sector, but their widespread use contributes significantly to environmental challenges, such as the short life and high daily production of HDPE milk bottles. This study therefore aims to find a solution to this plastic waste, focusing on mechanical recycling. A comprehensive characterization of this post-consumer recycled HDPE reveals significant PP contamination, which poses a significant barrier due to polyolefin incompatibility, a common challenge in mixed plastics recycling. To mitigate this, blending with virgin HDPE and the use of various compatibilizers were investigated to improve the recyclability of the material. Several extrusion cycles were performed to analyse the thermo-mechanical degradation and to measure the performance and stability of the blends. The environmental impact of incorporating recycled HDPE into new bottles was also evaluated. Comparative evaluations with virgin bottles show that incorporating 25% or 50% recycled HDPE in the bottle yields carbon footprint reductions of 3% and 14%, respectively. These benefits could amplify with a wind-powered supply chain and a 100% recycled content. The findings lay the foundation for future plastic recycling scenarios, including dedicated sorting for this waste stream, providing a pathway to address the environmental impact of HDPE milk bottle disposal through recycling practices.