High-Temperature Gasification for Material Recycling of Municipal Plastic Wastes

Did you know that only 9% of all plastic ever produced has been recycled? Today, the global recycling rate remains at a mere 9%, and even in Norway, a recycling leader, it's only 21%. This means that only about every fifth item we toss into the plastic recycling bin gets a new life. Why is plastic recycling so low? The process involves five main steps: collecting, sorting, shredding, melting, and creating new objects. Sorting is crucial because the final plastic object becomes a mix of all the plastic in the system. Plastic waste must be sorted by polymer type (e.g., PE, PET, PP, …) and colours to achieve good quality and save products. Plastic food packaging, widely used and a major contributor to plastic waste, possesses desirable properties like preserving aroma, keeping food fresh, and being resistant to tear and heat, as needed, for example, in microwavable food containers. Different plastic types are combined to achieve these tasks, with some packaging having up to 12 layers of base, glue, and diffusion barriers. While layering is essential for packaging, it impedes recycling due to the inability to sort these layers. A promising solution is high-temperature gasification. This technology rapidly breaks down plastics, as heat splits the long polymer chains into small gas molecules. The resulting gas can be used to create new, high-quality plastics of any kind. This process can even co-process biomass and plastic wastes and is hence a promising technology moving to a green economy and meeting our growing plastic demand without relying on fossil resources. The HighRec project aims to make this technology economically feasible by improving our understanding of the breakup process and the composition of the resulting raw gas mixture. New findings are implemented into process software to find energetic and economical optimal conditions for the entire process.

Only 9% of plastic produced since 1950 has been recycled. Most discarded plastics (73%) end up in landfills or are littered, leading to a constant flow of plastic in our oceans. Food packaging is a major contributor to plastic waste due to its short lifespan. Once discarded, food packaging forms a mixed, soiled, and unsortable plastic waste faction that, as of today, is not recyclable. High-temperature gasification is a promising method for recycling these mixed wastes. By subjecting the plastics to temperatures of 800°C, the organic structure of the plastic is atomized. The resulting product gas can be reacted into new mono- and polymers of the same quality as fossil-based plastics. Pilot plants have already demonstrated the technical feasibility of high-temperature gasification for mixed plastics and plastics/biomass mixtures. Further, researchers highlight its potential to phase out fossil feedstock by substituting it with bio-originated carbon sources. The HighRecproject aims to accelerate the technical, industry-scale implementation of high-temperature gasification by enhancing the predictability of engineering models. The models are targeted to describe the impact of the continuously varying feedstock on the product gases and the process downstream, such as the base chemical production. The project aims to describe the thermal break-up under instant heating and the interaction of the various polymers in composite films. First, fundamental insights are gained through molecular dynamics simulation. In the second step, findings are transferred to engineering models through a reaction mechanism and feedstock-sensitive databases for direct use in process modeling. The three resulting objectives of the HighRec projects are: 1) characterizing the decomposition steps of polymers and composite materials, 2) translating the description into feedstock-sensitive reaction mechanisms, and 3) creating product species maps for plastic and biomass mixtures.