Researchers at ExxonMobil, Trayak, and Michigan State University have published a study on the potential environmental impact of replacing polyethylene (PE) packaging with paper, glass, aluminium, or steel.
The study assessed five major packaging types, which account for about 60% of PE packaging sales in the United States: collation shrink films for bottled water and personal care products; stretch films for pallet wraps; heavy-duty sacks (HDS) for dog food, cement, etc.; non-food bottles for cosmetics, motor oil, paint; and flexible food pouches for juice, sauce, spices.
The researchers conducted a life cycle assessment (LCA) for these products in the United States, measuring potential environmental impact across four categories: Global Warming Potential (GWP), fossil energy use, mineral resource use, and water scarcity footprint.
Results show PE packaging has lower GWP, fossil energy use, mineral resource use, and water scarcity compared to alternatives in most applications. Moreover, substituting PE with alternative materials could lead to an average increase of 70% in GWP due to higher material weights and increased production emissions.
In particular, PE-based packaging used less fossil resources than alternatives in 14 of 19 product comparisons. In 16 of the 19 packaged product comparisons, PE yielded a lower GWP, water scarcity, and mineral resource use.
Glass, aluminium, and steel alternatives had the highest environmental impact due to their weight and energy-intensive production.
Paper-based alternatives sometimes had comparable or lower environmental impact but required more material per functional unit, leading to higher landfill emissions.
“Notably, those instances where PE did not have the lowest impact were typically found when comparing with lightweight paper alternatives that incorporated additional materials such as a plastic liner,” explained Rafael Auras, co-author and a professor at the Michigan State University School of Packaging. “These alternatives required the use of multiple materials to meet functional performance requirements, which could involve keeping a product stable or protecting against moisture.”
The comparison between PE stretch film and paper for pallet wraps, for example, showed PE has a GWP 70% lower than paper. End of life options for paper pallet wrap were largely responsible for the difference, as plastic-lined paper is mostly unrecyclable. In Europe, the PPWR’s reuse requirement for plastic pallet wrap is a topic of contention, with industry associations arguing it will force substitution with less environmentally friendly materials like paper.
The study also examined factors like post-consumer recycled (PCR) content, end-of-life disposal rates, and lightweighting. It found that increasing PCR content in PE packaging reduced environmental impacts. Higher recycling rates for paper and glass alternatives could mitigate some negative effects but were not enough to offset PE's advantages.
The authors recommended that policies aiming to replace PE packaging with alternative materials should consider full lifecycle impacts to avoid unintended consequences, e.g., shifting burdens to other environmental factors. Stakeholders should focus on improving PE recycling rates and reducing plastic waste rather than outright replacing PE with heavier, less efficient alternatives, the researchers said.
They declared potential competing interests through their employee relationship with ExxonMobil. The State University of Michigan noted the paper’s findings were critically reviewed by a panel of independent experts and determined to be in conformance with standards set by the International Organisation for Standardisation — ISO 14040 and ISO 14044, the international standards for principles, requirements, and guidelines for life cycle assessments.
The authors shared their findings in ‘Polyethylene packaging and alternative materials in the United States: A life cycle assessment’, recently published in Science of the Total Environment.