While beverage producers may still hold reservations about using recycled PET, according to KHS, a supplier of filling and packaging systems based in Dortmund, Germany, sees increasing bottle-to-bottle recycling rates as one sustainable solution to the challenges facing the industry.
The degradation occurring the mechanical recycling of polypropylene, polyethylene or polystyrene is irreversible. However, this is not the case for recycled PET. In fact, PET is currently the only recycled plastic approved as a food-contact material.
In Germany alone, about 93 percent of this material is recovered and reused. Nonetheless, in the past safety standards and quality issues were important factors inhibiting the wide-scale adoption of the use of recycled PET in bottles. Hence, following collection, many were — and still are — reprocessed into films and fiber, depriving the bottle-to-bottle recycling loop of a major source of raw material.
Now, however, the years of exploring technologies, trials and testing have borne fruit: as the company argues, from a technical standpoint there is "nothing preventing the global use of high percentages of recycled PET" for bottle production.
As a result, more and more beverage producers and brands are venturing in the direction of bottles made of 100 percent recyclate. Where this is not yet the case, various voluntary commitments have been announced: Poland Spring Brand 100% Natural Spring Water, one of the biggest water brands in the USA, plans to be the first major bottled water brand to reach 100% recycled plastic across its still water portfolio by 2022; Evian aims to use only recycled PET in their bottles by 2025. The other brands by Danone Waters, Pepsi and Coca-Cola plan to introduce a worldwide quota of 50 percent by that same year.
Their ultimate goal is for consumers to recognize the slight graying that can occur when PET bottles are recycled several times over as a hallmark of quality for sustainable packaging.
At KHS, recycled PET has long been a focus. The Group has been studying its use since 2012, and has a dedicated Bottles and Shapes service program that analyses the performance of recycled PET on the stretch blow molders and filling and packaging lines engineered by the Dortmund systems supplier.
“We run tests to qualify recycled PET so that we can tell our customers in advance which impact the material will have on the blow molder and bottle quality,” said Arne Wiese, product manager for Bottles & Shapes at KHS Corpoplast.
KHS also works closely with preform manufacturers, consulting with "all of the major plastics processors in Europe on this topic," said Wiese, in addition to liaising with various engineering companies on preform manufacture. Thanks to this close cooperation, data from the injection molding process can be used just in time to adapt the stretch blow molding process. This makes bottle production faster and more efficient and improves the quality of the finished containers.
An additional challenge is the color differences that occur from batch to batch of recyclate.
“Darker material absorbs heat better. The lower heating capacity requires less energy. This makes production more efficient yet means that adaptations must be made to the blow molding program on the stretch blow molder,” explained Wiese.
The intrinsic viscosity of the material is another issue. “The longer the recyclate is boiled under vacuum, the longer the polymer chains become. This means that the intrinsic viscosity increases and the quality improves. However, this results in additional costs which not everyone is prepared to invest,” Wiese added.
“Here, we have to come up with ways of redistributing the material from uncritical areas – the bottle base in the case of still water — to more critical zones.” Experience shows that manufacturers of premium brands — whose containers have thicker walls — have less cause for adjustment than discounters, where all of the lightweighting options have often been exhausted."
In collaboration with inspection technology manufacturer Agr International, KHS has now developed the Unit Mold Control, a digital, automated control system which regulates the blow stations on KHS’s InnoPET Blomax stretch blow molders individually.
Through continuous wall thickness inspection, it helps to control material distribution more precisely, reduces variations in the wall thickness by up to 30 percent and lessens any fluctuations in quality - especially relevant when using recyclate — during stretch blow molding.
According to Bottles & Shapes expert Arne Wiese there are no convincing arguments against the use of recycled PET in beverage bottles. The only relevant difference he sees between virgin PET and recycled material is the slightly darker color. This is a question of sorting, however — and only really visible in water bottles. In his view: “As far as the mechanics are concerned, there is nothing to stop companies converting to recycled PET, providing ideal conditions for the creation of a functioning circular economy.”