Study Finds Recyclability Issues In Weight, Labels for PET Bottles

For consumers, the recycling process begins and ends the moment they place a used plastic bottle in the bin.

For brands and bottle manufacturers, that process is considerably more complex. And as a movement towards sustainability and waste reduction continues to shape the industry, both are taking a closer look at how physical characteristics, design, and supplemental materials like ink and glue can affect the recyclability of bottles made with polyethylene terephthalate (PET).

Plastic Technologies Inc. (PTI), a firm that provides package design, development and engineering services to bottle manufacturers, explored this issue in a recent study analyzing how PET bottle weight affects performance, cost, and environmental impact, as well as how other design decisions influence recyclability.

The results concluded that ultra-lightweight bottles can negatively impact the effectiveness of recycling systems, while showing that the a majority of the bottles tested showed significant issues in recyclability, based on Association of Plastic Recyclers (APR) guidelines.

The study analyzed 500mL PET bottles, sold individually at room temperature, from the highest bottled water consumption regions where market-leading global brands are sold, including the U.S., Mexico, Europe (France, Italy, Switzerland), and India. Each were tested for weight, pressure, product volume, fill point, top load, thickness, section weights, color and closure types.

In an interview with BevNET, Marcio Amazonas, Director of Latin American Operations for PTI, said that study was partially intended to send a message to the category market leaders that good design, in terms of recyclability, can be a positive influence on the industry.

“We wanted to make this study as a competitive analysis to show who are the best brand owners in terms of a good design for recyclability,” said Amazonas. “It’s also sending a message to our own customers that we can help you improve your design.”

Weight is a crucial factor in determining bottle recyclability, but it has also increasingly become a way in which brands communicate a premium offering to consumers, and attempting to balance these two competing interests can make things even more complicated.

The samples evaluated from the U.S. reflected this stratification. Out of the seven, two samples came from premium-priced packages sold in 6-packs, which were around 22-23 g. The rest came from bottles of mid-range priced water, weighing 13-17 g, and value-priced bottles, weighing 7.5 to 8.5 g.

However, the study notes that the performance was not a direct correlation to the weight of the package.

“Sometimes the best ones were too heavy, so they are good in a way but they are not the most environmentally sound, because they could be lighter, Amazonas said. “But that’s a brand owner choice to position that brand as premium. So they want to go with the heavy plastic; that’s their call, but it’s not ideal for efficiency.”

Recycling performance for U.S. bottle samples

In recent years, some brands, such as Nestlé Waters, have adopted ultra-thin, super lightweight bottles based on the idea that they are more environmentally friendly because they require less energy to manufacture and transport. Yet according to Amazonas, recyclers are complaining about problems related to those bottles as well.

For example, lighter packaging can increase the number of bottles entering the recycling stream; Amazonas estimated that it could add 10,000 bottles per ton of recyclable materials.

Furthermore, when labels are sorted in a process called elutriation, they are soaked in a large tank of water to separate PET from polyolefins. Afterwards, an air current dries the materials and pushes the labels out of the chamber, but if the bottle is too light, it will be forced out as well.

“The yields suffer not only because of the potential presence of non-PET, but also mechanically speaking, the process is designed for a certain density that suffers with this lightweighting,” said Amazonas.

Besides weight, Amazonas noted that ink and label type as other potentially disruptive factors to the recycling process, as materials, colors, sizes and even the label application process all have an impact.

Of the seven U.S. samples tested, five had polymer labels, one had paper and one had a combination of the two. Five out of seven samples used a wrap-around label, while two used an adhered label.

All seven U.S. bottle samples tested had labels that caused color and clarity change in the wash, and label bleed was the most common issue observed. The study concludes that “the use of soluble inks and glues and the specification of the label substrate could have resulted in much better recyclability scores.”

“I think the ink is one of the big issues because it is so simple to resolve, and of course [the brands] are all competing on price and going for the cheapest thing,” said Amazonas, noting the presence of other non-PET contaminants in labels, such as PVC, that burn at different temperatures can cause recycling operations to reject certain bottles. “So sometimes it’s an economic decision on the design side to get to lower cost labels, inks and glues, and that’s what makes the design a little poor.”

In terms of solutions, Amazonas said the ideal PET bottle from a recyclability perspective would be clear with no colorants and none of the chemical additives that are sometimes used to create a barrier between the plastic and the liquid in bottles of milk or juice.

On a moral level, he noted the efforts of regulatory agencies like the Environmental Protection Agency (EPA) in promoting sustainable materials management, and said that brands will seek to capture the market of conscious consumers who expect recyclability to be a key component of a company’s mission.

“The heaviest volumes of bottle-to-bottle use is here, so we have all the good reasons to thank the market leaders like the guys we tested and we keep pushing,” he said. “They are not doing anything horrible, but if we don’t talk about it they will probably go with the most economic solution.”

Yet despite his deep knowledge of the industry, Amazonas said that the most important logistical piece of the recycling process is the simple act of the consumer throwing the bottle into the collection bin.

“If there’s no collection, there’s no recycling — so what’s the point?”