Compared to other materials, fibre-based packaging excels with its high recycling rate. Across Europe, they are recycled at a rate of 83 percent. The 4evergreen initiative wants to raise this bar to 90 percent. The alliance of nearly 100 companies, led by industry giants such as Stora Enso and Nestlé, aims to revolutionise packaging recycling for paper and cardboard. Different stakeholders from across the supply chain are therefore working together to develop recommendations that address aspects such as recyclability, testing methods, evaluation criteria and promoting innovation. This includes fibre-based packaging manufacturer Graphic Packaging International. Its Director of Business Development, Ralf Mack, explained in his presentation at FACHPACK 2022 how the participating companies are proceeding. As Mack emphasised, all members of the alliance are actively involved in the work by making important decisions, establishing test procedures and publishing results.
In order to achieve the ambitious recycling goals, working groups have defined four steps: First, an industry standard for recycling is to be established as a basis. Then the teams will examine how the knowledge gained will affect packaging design. In the third step, they look at optimising the sorting and collection of packaging materials. Finally, the experts look for possibilities for improvement.
The initiative has already published three papers with the renowned consultancies Smithers Pira, McKinsey and Berger. Initial standards have been defined in these. “However, these standards are still based on expert opinions and literature,” adds Mack. The goal is to rely on sound, evidence-based recommendations in the future. As a further milestone of the cross-company cooperation, Mack was able to present the initiative's first recycling guideline. It divides recycling standards into three categories with different processes: standard recycling facilities, deinking (ink removal) and specialised recycling facilities for heavily coated cartons. The guideline also defines what is meant by “recyclable”. Here the authors distinguish between “conditionally recyclable” and “completely recyclable”. According to Mack, however, it is difficult to clearly assign products to a category because various factors such as colours, film coatings and solvents can influence the recycling process. The group intends to work continuously on updating the guideline to include new materials and their recyclability. Tests have already been carried out and the next version of the guideline will take these results into account. Thus, deinking plants and specialised recycling processes will then also be included in the guidelines.
Up to 25 Recycling Runs are Possible
In the second presentation, Dr DI Rene Eckhart from the Technical University of Graz, Austria, started with the important question of whether fibre-based packaging can actually be recycled only six to seven times. This view has been held in many studies, mainly due to material losses on a laboratory scale. However, some research, including a study by Technical University of Darmstadt, Germany, has shown that paper can be recycled up to 25 times without a significant decrease in mechanical properties.
In a separate study, Prof. Eckhart investigated exactly how this behaves with folding boxboard. More precisely, an uncoated folding boxboard that has several layers. Since the carton is already made of recycled material, the trials started with a material that consisted of only 18 percent virgin fibre. Other important components in the recycling of fibre-based packaging are so-called ashes, pigments that are used in graphic papers to colour it white. In the laboratory tests, it was noticed that the loss of these fine pigments and other fine materials increases the mechanical strengths of the cardboard because they make it more difficult for the fibres to bond. To avoid these artefacts, a sorting process was carried out in which the ashes were reduced and the pigments washed out. At the same time, the degree of painting, i.e. the dewaterability of the pulp, was changed, making it easier to dewater. This did not affect the study as the main fibre material — the pulp fibres — remained intact. “The main problem was the loss of material, especially fine material, during sheet formation,” Eckhart reports. This was partially solved by white water recirculation, similar to that on a paper machine. This reduced the material loss per cycle to one percent. To rebuild the paper on a laboratory scale, the fibres could be used for new sheets.
The study confirmed that it is possible to achieve constant mechanical properties and strength over 25 cycles. Limiting factors, according to Eckert, are the collection rate, material loss during preparation and the structural integrity of the fibres.
While research into more sustainable plastic packaging is in full swing, some sustainability benefits can still be teased out of fibre-based packaging. The prerequisites for this are more efficient recycling processes and a better understanding of materials. But the development is far from over, as the research results show.
