Circularity of new composites from recycled high density polyethylene and leather waste for automotive bumpers. Testing performance and environmental impact

Eylem Kılıç; Pere Fullana-I-Palmer; Margalida Fullana; Marc Delgado-Aguilar; Rita Puig

doi:10.1016/j.scitotenv.2024.170413

Circularity of new composites from recycled high density polyethylene and leather waste for automotive bumpers. Testing performance and environmental impact

Sci Total Environ. 2024 Apr 1:919:170413. doi: 10.1016/j.scitotenv.2024.170413. Epub 2024 Feb 1.

Authors

Eylem Kılıç¹, Pere Fullana-I-Palmer², Margalida Fullana³, Marc Delgado-Aguilar⁴, Rita Puig⁵

Affiliations

¹ Leather Engineering Department, Ege University, 35100 İzmir, Turkey. Electronic address: eylem.kilic@ege.edu.tr.
² UNESCO Chair in Life Cycle and Climate Change ESCI-UPF, University Pompeu Fabra, 08003 Barcelona, Spain. Electronic address: pere.fullana@esci.upf.edu.
³ LEPAMAP-PRODIS Research Group, University of Girona, 17003 Girona, Spain.
⁴ LEPAMAP-PRODIS Research Group, University of Girona, 17003 Girona, Spain. Electronic address: m.delgado@udg.edu.
⁵ ABBU Research Group, Department of Industrial and Building Engineering, University of Lleida (UdL), 08700 Igualada, Spain. Electronic address: rita.puig@udl.cat.

PMID: 38309365
DOI: 10.1016/j.scitotenv.2024.170413

Abstract

New composite materials (suitable for automotive bumpers), composed of recycled high-density polyethylene (rHDPE) and leather buffing dust waste (BF) ranging from 20 to 50 wt%, were produced and investigated for mechanical properties. Optimal mechanical performance was achieved with composites containing 30 % wt BF. The environmental performance of automotive bumper production from both virgin and recycled HDPE reinforced with 30 % wt BF (HDPE-BF, rHDPE-BF) composites was compared to that of conventional polypropylene (PP) by performing a cradle to gate life cycle assessment. A component-based approach, instead of a comprehensive LCA assessment for the entire car was adopted using various functional units (FU) such as mass (FU₁), volume (FU₂), and volume of raw material fulfilling a specific impact strength requirement (FU₃), thus enriching the paper with methodological discussions. The rHDPE-BF system provided better environmental performance compared to the virgin PP system, when considering both mass and volume-related functional units, mainly due to the avoidance of virgin polymer production. Even with the inclusion of the use phase in FU₂ and a slightly higher density (+1.7 %) of composites than PP-based bumpers, the rHDPE system still provides better environmental performance (10 % less impact). The sensitivity analysis highlighted the significance of car type and final density of the bumper on the impact results. Finally, when using FU₃, due to its higher impact strength, HDPE-BF system is clearly the best environmental alternative (50 % less impact) followed by rHDPE-BF system. In all cases, rising the content of recycled materials in the bumpers increases its circularity. The paper illustrates the importance of selecting a suitable functional unit, based on a specific application (i.e., automotive bumpers), to evaluate the environmental impact of new composite materials in comparison to traditional options. Expanding the assessment to encompass multiple functions provides a more accurate portrayal of reality but also introduces greater result uncertainty.

Keywords: Car bumper; Environmental comparison; Leather waste; Life cycle assessment (LCA); Recycled high density polyethylene (rHDPE) composite.