ORACLE

Plastic is one of the most significant innovations of the 20th century and, thanks to its versatility, it has become essential to our lives.
However, each fragment of plastic we have employed or relinquished has indelibly imprinted its presence, and in recent times, there have been increasing discussions about the consequences this may have on the planet and on future generations. A closer and more comprehensive look reveals that the advantages of using this material far outweigh the disadvantages. For this reason, it is unthinkable to eliminate plastic but, rather, it is necessary to understand how to make its use more sustainable. In this sense, recycling undoubtedly plays a key role in the ecological transition. While many plastics have been following a circular economy path for years, extruded polystyrene (XPS) is hardly reused at the end of its life. This becomes a major issue considering that polystyrene is the sixth largest polymer in the world in terms of production. Indeed, the remarkable properties of this material, including lightness, flexibility, water resistance and insulation capacity, make it an ideal material for food containers and, consequently, it is widely used in packaging and disposable products. Unfortunately, these are not recycled or, at least, cannot be reused for food-contact applications. As a result, 95% of post-consumer XPS waste ends up in landfills, with a huge environmental impact. To tackle this problem, the recycling route seems to be the most reasonable one, reducing waste pollution and decreasing the production of virgin plastics, thereby safeguarding the fossil resources from which they are created. As with other plastics, recycling can be mechanical or chemical. In the case of PS, however, the high temperatures of the latter could degrade the material, and for this reason, mechanical recycling is preferred. Nevertheless, there are neither regulations nor available experimental data regarding the recycling of this material for food contact applications, unlike other plastics such as polyethylene terephthalate (PET).
In this context, a close collaboration between Alta Scuola Politecnica and GreenChemicals gave birth to ORACLE, whose name is representative of the research question: “Can pOlystyrene XPS food tRAys be recyCLEd?”. Indeed, the team’s goal is to respond to all these challenges through a holistic approach and to create a comprehensive and sustainable solution. This, by meticulously exploring the technical and regulatory aspects of the problem, and then designing a feasible and efficient recycling process for XPS. The ultimate aspiration is to secure approval from the European Food Safety Authority (EFSA), allowing the recycled polystyrene to be safely utilized in food contact applications.

With this initiative, ORACLE is committed not only to the mitigation of the environmental impact of plastic waste but also to the contribution to the circular economy model. Given the significant regulatory and technological gaps that the project seeks to bridge, the team have structured its work into two basic and distinct phases. As a first step, it was necessary to understand what regulations and regulatory procedures govern plastic recycling processes, particularly in the food packaging sector. Since there are no specific information regarding PS recycling, during the first few months the ORACLE team analysed the official documentations related to recycled plastic materials and articles intended to come into contact with foods (EC regulations 2022/1616 and 1935/2004) taking them as a reference to understand both the requirements in terms of contaminant threshold values in recycled material as well as the bureaucratic procedure to follow when proposing a new technology. Once this was clarified, the technological process for recycling XPS was defined through a collaboration with Gamma Meccanica. Specifically, an efficient method for removing contaminants from post-consumer XPS packaging was identified using supercritical CO2 injected into the recycling line.

For the reintroduction of recycled plastic in contact with food, the focus of the process is on the decontamination from hazardous substances. Nevertheless, the establishment of a definitive collection and sorting system for XPS remains pending. Therefore, the acquisition of post-consumer material has been facilitated through the efforts of Gruppo Happy, who has undertaken a dedicated collection initiative. After this collection process, the postconsumer material has undergone an artificial contamination due to the introduction of appropriate substances as part of the procedural steps, at Gamma Meccanica’s facilities.
Once pollutant levels compatible with those in the waste were reached, extrusion and decontamination using CO2 were carried out.
Measurements at the end of the process, aimed at quantifying the efficiency of pollutant removal, demonstrated the feasibility of the process. Moreover, it was shown through an economic analysis that the specific cost (€/kg) of recycled XPS was fairly lower than that of virgin material, making the recycling route worthwhile not only environmentally but also economically. Although significant decontamination progress has been made, the current efficiencies are insufficient for obtaining EFSA certification. Furthermore, given the lengthy 42 to 78-month certification process timeline, alternative non-food sector applications for recycled XPS were identified. Indeed, Swisspor conducted tests for insulation panel production, and in collaboration with Selit, they explored underfloor layer applications using recycled XPS. The tests provided a positive outcome and proved the process to be already capable of producing a secondary raw material suitable for the utilization in the construction sector. All in all, in a world facing the problem of creating a sustainable future, the ORACLE project shed light on the feasibility of XPS recycling, offering a tangible technological solution. In particular, the results obtained through the process confirmed that the project is on the right track, confirming CO2 technology as probably the most suitable technology for XPS mechanical recycling. The decontamination rates downstream of the process are undoubtedly promising, although not yet sufficient to obtain the certification that would allow the material to be reused for food contact. At the same time, it would be unthinkable to obtain definitive results only after the first experimental trials. For this reason, further tests are planned for the future, in which the optimal number of degassing operations, pressure and CO2 flow rate will be defined, with the ultimate goal of applying to EFSA for certification and finally giving new life to the polystyrene material.