For the Package Engineer: Why PET Wins Every Time

Contributed by NAPCOR Technical Consultant, Dave Cornell

“We fought these fights a generation ago. Apparently, winning did not end the fight.” – Dave Cornell

April 29, 2020 – Dave Cornell is a technical resource for NAPCOR, a plastics Hall of Fame member and all-around chief plastics expert who reflects on PET’s image and why we continue to fight the environmental battle.

Before we turn to environmental impacts, let’s begin by looking at the performance criteria that make PET such an attractive packaging material in the first place. The economics work for PET, and the cost per bottle has dropped over the years. It’s also lightweight, so when you factor in transportation costs it is especially appealing as an alternative to glass. Though aluminum cans are less expensive to make (roughly comparable to the cost of producing PET containers of similar size), larger PET bottles are more economical than aluminum per unit volume of the fluid packaged.

PET is unmatched in terms of design and performance versatility. PET barriers work better than those of HDPE, and may be enhanced. Fill temperature can be raised (with some investment), and PET can be aseptically filled. There is a plethora of blown and molded PET containers in the marketplace that demonstrate its vast design options. Glass, in comparison, is moderately versatile, while aluminum is more limited. Aluminum cans cannot be reclosed, and they also mask their contents, while PET is transparent. Paper alternatives to PET are extremely limited in design.

In terms of safety, shatterproof PET wins over glass when it comes to breakage (and reduces the need for secondary packaging). There have been attempts by critics over the past forty years to show that PET is toxic, all to no avail. PET does not contain endocrine disruptors (no BPA or BPS). The cap closure on PET bottles is hygienic and protects the consumer from direct contact with anything the package may have been subjected to on the way to its destination, as opposed to the tops of aluminum cans which are exposed to the elements.

Life cycle assessment (LCA) studies show that PET beats glass, aluminum, and steel in terms of energy consumption and greenhouse gas emissions. The greenhouse gas issue is well-understood, but there tends to be confusion in interpreting the energy results of LCA studies (due to lack of clarity regarding the distinction between inherent energy that remains embedded in the packaging material versus expended energy – which is what we really care about – required to produce the package). If water consumption and land usage factors were included in these LCA analyses, paper alternatives to PET would not fare well, and the same is likely true for bioplastics.

PET is not biodegradable, but this is really a good thing, because it allows for recycling into new products again and again (more on that below). It’s commonly thought that biodegradable plastics solve waste management problems, but the reality is that composters do not want “bioplastics” as feedstock because they take much too long to decompose. The idea that nature will take care of any biodegradable plastic litter in the environment is misguided, and potentially destructive if it encourages littering. In the near term, biodegradable plastic litter is just as permanent as non-biodegradable plastic litter.

Unlike other plastics, PET can be recycled repeatedly – and it is. The recovery rate for PET is far higher than that of other resins, but it is often lumped in with all other plastic to the detriment of this recycling story. Globally, 53% of PET bottles are recycled (Wood Mackenzie, 2018). The US has one of the worst PET recovery rates in the world at 29%, but this still far exceeds that of most other plastics. There is huge opportunity to increase the amount of PET that gets recycled, which is why NAPCOR has begun the Positively PET campaign to educate consumers and encourage them to improve their PET recycling habits.

Not only is PET highly recyclable, but it’s also suited for reusable packaging models. Refillable PET containers do exist, and they beat glass refillables in every category other than scratch resistance and wash temperature (which must be carefully controlled to keep PET bottles from warping). If refillable options are more fully developed, PET can have an even more prominent place in the circular economy than is afforded by its recyclability alone.

So, on a rational basis, PET packaging is still the right choice. But, the fight goes on.