Issue 06/2022

Basics Advanced

Basics Advanced Recycling – overview of the most common technologies Industry experts at the nova-institute have worked tirelessly to provide a structured, in-depth overview and insight into all advanced recycling technologies. While a full report on these technologies is available it can be quite daunting for beginners to the topic – hence here a quick overview and short explanation of the most common advanced recycling technologies. Depending on the technology various products can be obtained which can be reintroduced into the cycle at various positions in the value chain of plastics (Figure 1). Below, the capabilities as well as the feedstocks and products of each technology are described in more detail. Figure 1: Full spectrum of available recycling technologies divided by their basic working principles. Dissolution (Figure 2) is a solvent-based technology that is based on physical processes. Targeted polymers from mixed plastic wastes can be dissolved in a suitable solvent while the chemical structure of the polymer remains intact. Other plastic components (e.g. additives, pigments, fillers, non-targeted polymers) are not dissolved and can be cleaned from the dissolved target polymer. After cleaning an anti-solvent is added to initiate the precipitation of the target polymer. After the process the polymer can directly be obtained, in contrast to solvolysis, no polymerisation step is needed. The solvent-based solvolysis (Figure 3) is a chemical process based on depolymerisation which can be realised with different solvents. The process breaks down polymers (mainly PET) into their building units (e.g. monomers, dimers, oligomers). After breakdown, the building units need to be cleaned from the other plastic components (e.g. additives, pigments, fillers, non-targeted polymers). After cleaning, the building units need to be polymerised to synthesise new polymers. With pyrolysis (Figure 4), a thermochemical recycling process is available that converts or depolymerises mixed plastic wastes (mainly polyolefins) and biomass into liquids, solids, and gases in presence of heat and absence of oxygen. Obtained products can be for instance different fractions of liquids including oils, diesel, naphtha, and monomers as well as syngas, char, and waxes. Depending on the obtained products new polymers can be produced from these renewable feedstocks. Gasification (Figure 5) represents another thermochemical process that is capable to convert mixed plastics wastes and biomass in presence of heat and oxygen into syngas and CO 2 . Enzymolysis represents a technology based on biochemical processes utilising different kinds of biocatalysts to depolymerise a polymer into its building units. Being in early development the technology is available only at lab-scale. The market study “Mapping of advanced recycling technologies for plastics waste” provides an in-depth insight into advanced recycling technologies and their providers. More than 100 technologies and their status are presented in detail which also lists the companies, their strategies, and investment and cooperation partners. The study is available online for EUR 2,500. www.renewable-carbon.eu 54 bioplastics MAGAZINE [06/22] Vol. 17

By: Lars Krause, Senior Expert – Technology & Markets Basics nova Institute Hürth, Germany Figure 2: Process diagram showing the inputs and outputs of the solvent-based dissolution process. Figure 4: Process diagram showing the inputs and outputs of different secondary valuable materials (SVM) from the pyrolysis process. The main products are usually pyrolysis oil (via thermal-/catalytic-/hydro-cracking) or monomers (via thermal depolymerisation) Adapted from Stapf et al. (2019). Figure 5: Process diagram showing the inputs and outputs of secondary valuable materials (SVM) from the gasification process. Figure 3: Process diagram showing the solvent-based solvolysis of PET including the inputs and outputs (polyols, bis(hydroxyethyl)terephthalate (BHET), dimethyl terephthalate (DMT), terephthalic acid (TPA), and TPA amide). Adapted from Aguado et al. (1999). References Aguado, J., Serrano, D. P. and Clark, J. H. 1999: Feedstock Recycling of Plastic Wastes The Royal Society of Chemistry, Cambridge, United Kingdom. Stapf, D., Seifert, H. and Wexler, M. 2019: Thermische Verfahren zur rohstofflichen Verwertung kunststoffhaltiger Abfälle. Energie aus Abfall, Band 16. Thiel, S., Thomé – Kozmiensky, E., Quicker, P. and Gosten, A. (Ed.). Thomé-Kozmiensky Verlag GmbH, Neuruppin, Germany. bioplastics MAGAZINE [06/22] Vol. 17 55