Basics Recycling By
Basics Recycling By Michael Thielen in cooperation with Stephan Kabasci, Markus Hiebel Fraunhofer UMSICHT Oberhausen, Germany In an insightful article on page 20, Michael Carus outlines his ‘Renewable Carbon Strategy’ in which he not only makes a compelling case for the need to abandon the use of fossil carbon but also describes the steps towards transitioning to the use of renewable carbon [1]. One of the three pillars of this approach is the recycling of already existing plastics (and organic chemistry products). In the present article, however, I would like to focus on the recycling of bioplastics. But first, here is quote on the recycling of plastics in general. “Plastics recycling as an elementary component of a circular economy is not a new topic. However, an awareness has developed that the responsibility no longer lies exclusively with the recyclers or waste management companies, but rather along the entire value chain. Instead of individual activities or ‘island solutions’, various actors are increasingly joining forces. Thus, a ‘design for recycling’ only makes sense if the relevant products are indeed actually recycled and if the design of the new product enables the use of the resulting recyclates, ultimately allowing these recyclates to be reused in a new application” [2]. And, as I already commented in my “Dear Readers” in issue 05/2019: … if products are recyclable, but don’t actually get recycled, the benefits in terms of sustainability are zero. Recycling of bioplastics The following elaboration is based on a position paper of Fraunhofer UMSICHT (Oberhausen, Germany) which can be downloaded in full for free [3]. Bioplastics are either biobased or biodegradable or both. Biobased but non-degradable plastics make up approximately 45% of all bioplastics (cf. graph on page 10). On the one hand, there are the so-called drop-in solutions which are chemically identical to their fossil-based counterparts, such as fully biobased PE and PP, or the partially biobased PET (20% biobased carbon) and bio-polyamides (PA 4.10, 6.10 etc.). On the other hand, there is the relatively new, fully biobased polyethylene furanoate (PEF), which might be an alternative to PET. Biobased and biodegradable bioplastics with significant market relevance are polylactic acid (PLA), polyhydroyalkanoates (PHA) and thermoplastic starch blends. Of the total volume of plastics produced today (about 360 million tonnes in 2018 [4], all bioplastics together account for about a 0.055% share. Around half of that goes into packaging applications (cf. graph on page 11). Use is followed by disposal. In the case of bioplastics, “thermal recycling”, i.e. waste to energy incineration can be considered as a climate neutral or carbon neutral disposal route. However, recycling, whether mechanical (see e.g. [5]), chemical (see e.g. [6]) or solvent-based recycling (see e.g. [7]), in particular for the group of biobased and non-degradable bioplastics, offers another important recovery route that should be prioritized before incineration. However, before plastics -including bioplastics- can be recycled, they must first be sorted. Here automated methods, such as the fast, contactless molecular recognition of plastics using such methods as spatially resolved near infrared spectroscopy [NIR] and others can help, as they can also be applied to bioplastics. Newer methods using laser spectroscopy and the method of hyperspectral imaging have refined and extended the possibilities, so that even black plastics can be detected. The spatial resolution of individual plastic residues on a sorting belt has also been further enhanced, so that sorting at flake level is now state of the art. New developments such as electro-hydraulic comminution will bring the separation of galvanized plastics (metal-plastic composites) within reach in the future (find detailed literature references in [3]). Factors limiting the possibilities of automated sorting include, among others, composite materials such as multilayer films or material combinations, e.g. plastic with paper labels. With sufficiently pure sorting fractions, material combinations can also be largely separated through downstream processes, as shown by the separation of PET bottles into caps and PET flakes and the colour sorting of the PET flakes [8]. However, sorting mixed residual material streams from recycling bins or the German Yellow bin/sack recycling scheme remains the greatest challenge in dealing with packaging waste. Economic factors ultimately dominate the quality (purity) of a sorting fraction. Due to their low volumes, new types of plastic often cannot be sorted economically as a separate fraction and are either discharged for disposal (preferably incineration) or can contaminate other fractions. However, the contaminating effect of biobased plastics is generally no greater than that of the fossil-based impurities already present, according to research conducted at Wageningen University [9]. Conclusions and outlook The recycling of bioplastics is possible. In sum, all plastic products, including those made of biobased plastics or biodegradable plastics, should be fed into a target-oriented waste management system. The littering of the environment with plastics, whether fossil-based or biobased, degradable or non-degradable plastics, is a social and regulatory problem. Public information about the correct or incorrect handling of plastics - and in a broader sense the handling of all resources - at the end of their utilization phase needs to be fundamentally intensified. 40 bioplastics MAGAZINE [01/20] Vol. 15
Basics Products and materials must be designed as far as possible in a way that allows them to be recycled. The range of plastics used today and the use of multilayer composites, especially for short-lived products such as packaging, must therefore be reconsidered. Material combinations that are difficult to recycle should be avoided. These include, for example: • - material mixtures (e. g. multilayer films with e.g. barrier layers, that cannot be separated) • - metal-plastic combinations (e.g. with aluminium as barrier layer) • - plastic-paper combinations (e. g. through non-removable labels) • - material combinations that are difficult to detect (due to product design) Other design criteria for recyclability are the ability of the packaging to be emptied of residues and residue-free separable components (e. g. lids for yoghurt cups). Materials with very good barrier properties are often used for food packaging. More intensive research is needed on how these solutions can be achieved without the use of multilayer composites. The use of recycled material in food contact, however, is a special challenge. The use of renewable raw materials is an important strategic route due to the inevitable long-term move away from fossil raw materials and should certainly continue to be pursued, regardless of biodegradability. Deposit solutions, e. g. for PET bottles, lead to high return rates (up to 95-99 %) at high purity and recycling rates. An expansion of the deposit system to other materials should be considered openly and transparently with all stakeholders, taking into account the costs and benefits. New deposit systems based on biobased plastics from the outset could increase market penetration. Bioplastics currently account for well under 1 % of plastic waste. The purity requirements for the sorting fractions, e. g. by Der Grüne Punkt - Duales System Deutschland GmbH (DSD), allow far higher impurities. Studies have shown that hardly any deterioration in properties of post-consumer recyclates is noticeable in the sorting fraction in the presence of a low bioplastics content. Further investigations in this area would seem warranted. These facts and recommendations (and more, see [3]) form the basis for technical and social innovations in the field of bioplastics that are being developed at Fraunhofer UMSICHT. References (more references in [3]): [1] Carus, M.: Renewable Carbon Strategy, bioplastics MAGAZINE, Vol 15, issue 01/2020 [2] Endres, H.J.: Aufbruch ins Zeitalter der Kreislaufwirtschaft, KUNSTSTOFFE 1/2020, Carl Hanser Verlag, München, Germany [3] Kabasci, S.; Hiebel, M.: Fraunhofer UMSICHT takes position- Topic: Recycling of Bioplastics (pdf), 2018; https://tinyurl.com/UMSICHT-recycling [4] N.N.: Plastics the facts 2019, PlasticsEurope¸ https://www.plasticseurope. org/de/resources/publications/2154-plastics-facts-2019 [5] Thielen, M.: Mechanical recycling of bioplastics, bioplastics MAGAZINE, Vol 13, issue 02/18 [6] Thielen, M.: Capacity for PLA Feedstock Recovery to Expand Significantly, bioplastics MAGAZINE, Vol 6, issue 06/10 [7] Fell, T. et.al.: Sustainable recycling strategies for products and waste streams containing biobased plastics – SustRecPLA; https://www.ivv. fraunhofer.de/en/recycling-environment/packaging-recycling/sustrecpla. html [8] N.N. (Sesotec GmbH, Schönberg, Germany): Plastic: part of the problem… part of the solution - Part 3: Sorting technology; https://www.sesotec. com/emea/en/resources/blog/plastic-part-of-the-problem-part-of-thesolution-part-3-sorting-technology [9] van den Oever, M.; Molenveld, K.; van der Zee, M.; Bos, H.: Bio-based and biodegradable plastics – Facts and Figures; https://library.wur.nl/ WebQuery/wurpubs/fulltext/408350 Info: 1: The study can be downloaded form https://tinyurl.com/UMSICHT-recycling www.umsicht.fraunhofer.de bioplastics MAGAZINE [01/20] Vol. 15 41
