The development of sustainable packaging is a topic that has gained notoriety in recent years, but simply switching from plastic to other alternatives could be even more damaging to the environment. Researchers from ExxonMobil, Trayak, and Michigan State University published a study on the potential environmental impact of replacing polyethylene (PE) packaging with paper, glass, aluminum, or steel.

Packaging comparison: Which materials have the lowest impact?

The researchers analyzed five types of packaging that account for approximately 60% of PE sales in the United States:

• Shrink wrap films for bottled water and personal care products
• Stretch wrap films for pallet wrapping
• High-strength bags (HDS) for dog food, cement, etc.
• Non-food bottles for cosmetics, motor oil, paint
• Flexible pouches for food such as juices, sauces and spices

The results show that PE packaging has lower GWP, fossil energy use, mineral resource use and water scarcity compared to alternatives in most applications. Furthermore, replacing PE with alternative materials could lead to an average 70% increase in GWP due to the higher weight of the materials and increased production emissions.

In particular, PE-based packaging used fewer fossil resources than alternatives in 14 out of 19 product comparisons. In 16 out of 19 packaged product comparisons, PE had lower GWP, water scarcity and mineral resource use.

What about alternatives to PE?

The researchers identified that:

• Glass, aluminium and steel have a higher environmental impact due to their weight and the high energy required in their production.
• Paper packaging can be a viable alternative, but it requires more material, increasing carbon emissions.
• Plastic-coated paper, used in many applications, is difficult to recycle and generates more waste.

For example, the comparison between PE stretch film vs. pallet wrapping paper showed that PE has 70% lower GWP, as plastic-coated paper is difficult to recycle.

“It is worth noting that those cases where PE had the least impact were typically found when comparing with lightweight paper alternatives that incorporated additional materials such as a plastic coating,” explained Rafael Auras, co-author and professor at Michigan State University’s 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 it against moisture.”

The comparison between PE stretch film and pallet wrapping paper, for example, showed that PE has a 70% lower GWP than paper. End-of-life options for wrapping paper pallets were largely responsible for the difference, as plastic-coated paper is mostly non-recyclable. In Europe, the PPWR reuse requirement for wrapping plastic pallets is a matter of controversy, with industry associations arguing that it will force substitution with less environmentally friendly materials such as paper.

The study also examined factors such as 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 the advantages of PE.

How to improve the sustainability of PE packaging?

Now, addressing the issue of packaging sustainability, the study suggests that instead of banning PE, strategies should focus on:

• Increasing post-consumer recycled (PCR) content in PE packaging.
• Improving recycling rates to reduce plastic waste.
• Optimising packaging design to make it even lighter and more efficient.

The researchers concluded that replacing PE with alternative materials could shift the environmental impact to other areas rather than reducing it. They further emphasised that any changes in packaging policy should be based on a full life-cycle analysis to avoid unintended effects.