Emilia Kauppi, a doctoral researcher at Aalto University, is on a mission to tackle one of today’s most pressing environmental challenges: improving the efficiency and quality of plastic recycling, particularly in the context of liquid packaging board (LPB). Her research, which is halfway through its course, aims to define how wood-based fibres and plastics can be separated and recycled as high-quality materials.
The project, known as SEREPLAS, is closely linked to initiatives at Stora Enso, Valmet and Aalto University’s Bioinnovation Centre. While being connected to the ReMatCh (Recycling Material Challenge) project carried out under the SPIRIT programme, SEREPLAS shares its goal of enhancing plastic recycling. ”The focus is on energy-efficient methods to separate fibres from plastic-coated cardboard, ensuring that both materials can be recycled at the highest possible quality,” Emilia Kauppi explains.
Addressing the recycling challenge of liquid packaging board
Liquid packaging board, commonly used in beverage cartons, poses unique recycling challenges as its plastic coating is tightly adhered to the cardboard – a feature ensuring good properties for the product. The standard process for recycling liquid packaging board (LPB) begins with hydropulping, where mechanical energy in water is used to separate the fibre component into a slurry for further processing into new paper. Meanwhile, the plastic remains on the sieve of the hydropulper. This reject fraction, which consists of the plastic and aluminium layers of the LPB, is commonly referred to as polyAl. In Finland, non-aseptic packaging without aluminium is more common compared to countries like Germany, where aseptic, aluminium-containing LPB is used more frequently. For LPB, this process requires more energy than standard paper due to additives and plastic.
”The main challenge lies in separating the fibres from the plastic coating,” she says. ”Fibres are tightly bound to the plastic, which makes the separation process more demanding in terms of energy and time.” Moreover, while the fibres are often recycled into new paper products, the plastic fraction is typically incinerated, a practice Kauppi describes as ”wasteful” given the material’s potential for reuse.
Innovative pre-treatment techniques
Kauppi’s research focuses on improving the pre-treatment of LPB to make the pulping process more efficient. Preliminary findings have shown promising results. Her tests have shown that prewetting liquid packaging board (LPB) prior to hydropulping significantly accelerates fibre disintegration and improves fibre-plastic separation, thereby increasing process efficiency. Among the prewetting methods tested, perforation and hydraulic pressure have shown the most promising results, with the potential to reduce energy consumption by up to 50% on a large scale.
In her tests, the high-consistency pulper has proven to be significantly more energy-efficient than the low-consistency pulper for processing liquid packaging board (LPB). The key differences lie in the rotor and pulper design, as well as the higher fibre consistency used in the process. With prewetting, the pulping process can be accelerated, as wet carton is weaker than dry and therefore disintegrates more quickly. While this wetting typically occurs during the hydropulping, it can be shifted outside the pulper through prewetting.
Collaboration and practical applications
The SEREPLAS project is supported by industry leaders such as Valmet and Stora Enso, as well as academic expertise from Aalto University. Valmet, a global supplier of process technologies, provides the necessary equipment and technical knowledge for pilot testing. ”Valmet has been in a key role in helping me test different pulping methods and scale up the process,” Kauppi says. Stora Enso, one of the world’s largest producers of renewable packaging materials, contributes its expertise in cardboard production, ensuring that the solutions align with real-world requirements.
Kauppi’s research ties into the goals of the ReMatCh project, which seeked to find innovative ways to repurpose fibres recovered from liquid packaging board. “The ReMatCh project is a future-oriented large-scale research project and platform lead by Stora Enso in the area of sustainable and efficient material use and re-use. Science and applied research are an important part of the route to create new knowhow in recycling of materials and related effective processes. Effective and high-quality recycling will have very important role in the future,” says Jari Räsänen from Stora Enso.
A vision for the future
Kauppi envisions a future where the technologies developed through her research lead to substantial benefits on an industrial scale and generate new knowledge that can contribute to the advancement of technology. ”The ultimate goal is to develop technologies that make it economically and environmentally feasible to recycle both fibres and plastics on a large scale,” Kauppi notes. ”My dream outcome is to see practical applications that yield high-quality recycled paper and plastic, and significantly reduce waste,” she shares.
Although similar recycling challenges are being addressed in other parts of the world, such as in Germany, where aluminium-containing packaging is mechanically separated and recycled, Kauppi believes her work offers unique solutions. ”Hydropulping is the most common recycling method, and we have thoroughly examined this process. Other methods, such as solvent-based (dissolving) techniques, also exist. Another ongoing project is examining various existing processes from a life cycle assessment (LCA) perspective.,” she says.
As Kauppi continues her research, supported by the guidance of her supervisor prof. Jouni Paltakari at Aalto University and collaboration with industry and academic partners, the potential for advancements in plastic and fibre recycling is clear. In her previous article, it was estimated that on a large scale, using perforation combined with hydraulic pressure could reduce pulping energy consumption by 50%. Additionally, this approach could also lower the energy demand in the refining stage. Emilia sees herself as a reflective, critical and solution-oriented person who wants to understand different phenomenon on a profound level – characteristics that are definitely progressing her doctorate thesis and yielding results.
Sanna Martin from Borealis concludes: “Plastic layer is crucial in paper-based packaging for moisture and gas barriers, ensuring product freshness and durability. I’m eager to see Emilia’s work on improving recyclability by also capturing the plastic component to recycling scheme.”