Plastics recycling and hazardous substances – Risk Cycle 2026

The carbon that is currently being downcycled does not contribute to the defossilization of the chemical industry; in fact, it is a waste of carbon.

by Uwe Lahl, Barbara Zeschmar-Lahl

Introduction 

Material recycling of plastics involves processes and concepts in which the polymer molecule of end-of-life plastics, i.e., waste products, remains largely intact. In addition to the classic mechanical processes, in which plasticization takes place again after collection and sorting, there are processes that dissolve the polymer molecule and then precipitate it again (solvolysis), which are on the borderline with chemical recycling¹. Chemical recycling – which is not discussed further in this paper – breaks down the polymer molecule to varying degrees and then rebuild polymers or other materials from the resulting fragments. 

For material-based plastic recycling, the qualities achieved by the recycled materials and their potential applications are relevant. The quality of the recycled materials and their (possible) areas of application are interrelated. The authors make a broad distinction between upcycling, recycling, and downcycling. 

• Upcycling is achieved when the recycled materials are of such high quality that they can be processed into a product of higher value than the original products. 
• Recycling refers to cases in which a recycled material of the same substance replaces a new material (hereinafter referred to as "virgin plastics") of the same quality. Therefore, these recycled materials must be of approximately the same quality as virgin plastics.  
• In downcycling, the quality of the recycled materials only allows the plastic to be used purely as a material in products with lower requirements in terms of purity and quality of the material and/or performance of the product. These are usually products that are used outdoors and could also be made of concrete, asphalt, wood, or iron. 

The quality of recyclates for material recycling is defined by the purity of the input at the filling opening of the extruder. The renewed plasticization results in intermediate products that are traded (e.g., granulates) or processed directly (possibly in mixture with virgin plastics and recycling additives) into end products. Purity refers primarily to the respective polymer molecule, but also to the additives and other impurities contained in the input. A level of purity that allows upcycling of the recyclate is difficult to achieve. For level-equivalent recycling, it is necessary that the starting material for the recyclate is a polymer fraction as homogeneous as possible (> 95%, preferably > 99%), which – as a rule – cannot be achieved with today's sorting processes. 

Only separate collection of used products can roughly deliver this quality, as the example of single-use PET beverage bottles shows. This also fulfills a second prerequisite for recycling: the additives in the recycled materials are similar or identical to those in virgin PET. Recycling is particularly possible for raw materials from the pre-consumer sector. For example, cutting scraps and similar waste from the manufacture of plastic products are very homogeneous and similar in terms of additives. These types of waste can be recycled at the same level. 

The quality of today's sorted fractions from post-consumer packaging in Germany or Austria regularly does not allow for recycling, but only downcycling. The quality of the sorted fractions ranges from 80 to 85% for the respective polymer, sometimes even lower. Several fires in various sorting plants – caused primarily by the uncontrolled return of devices with lithium batteries and loose rechargeable batteries [2] have reduced plant capacities in Germany, forcing the remaining plants to operate at high throughputs, which in turn further deteriorates quality. 

Added to this are difficulties resulting from packaging design that cannot be solved by today's sorting and recycling techniques. One example of these difficulties is yogurt cups: these are increasingly being wrapped in a (wet-strength) paper sleeve. This saves plastic – the polystyrene content is reduced by about 20%, but about three times as much cardboard is needed to replace the polystyrene saved [3] – and consumers are led to believe that this is environmentally friendly packaging. However, the opposite is true: the (composite) cup can no longer be sorted as polystyrene in sorting plants. Either it is added to the film fraction via wind sifters (because it is so light) and contaminates it, or it ends up in the liquid carton/cardboard fraction and contaminates that. As a result, many sorting plants are increasing the screen sizes of their inlet screen drums in order to sort out these materials at the same time – primarily as sorting residues for thermal recycling. 

Another example is multilayer films. This type of packaging is on the rise because it ensures high quality food presentation in supermarkets, for example, and has become indispensable in this sector. Around one third of packaging consists of multi-layer films. This development is a minor disaster for material recycling because there is no recycling solution for these films. Even downcycling reaches its limits here. The multi-layer structure can also be found in another type of packaging. There are multi-layer plastic bottles, one of which has a thin glass layer, or – for fruit juices that are sensitive to oxidation – with a middle layer of polyamide (PA) or ethylene vinyl alcohol copolymer (EVOH). 

A third example is black plastics, which is widely used in both households and industry. This plastic cannot be identified by polymer type using the techniques commonly working in sorting facilities today – NIR light (near-infrared) –, because it absorbs the light and leaves nothing to be detected. 
 
Downcycling is worse for the environment than high-quality recycling (e.g., in terms of direct greenhouse gas emissions [4]). When mixed waste plastics are mechanically recycled without first being sorted by polymer type, the material quality decreases significantly in the first cycle. Further material recycling is then usually no longer possible, and the material must be sent for energy recovery (waste-to-energy). The decline in quality is also reflected in the price: in downcycling, the recyclates replace, for example, concrete, which costs the equivalent of approximately 7–8 cents/kg² on the market (e.g. [5]), or low-quality wood with a price (e.g. [6]) of the equivalent of approximately 20–40 cents/kg³. In high-quality recycling, on the other hand, virgin plastics are replaced at a significantly higher price. 

The quality of the recycled material is sometimes so poor that even the low prices for the respective recycled materials, e.g., from post-consumer waste [7], can no longer be realized on the market. In many cases, additional payments are even made; the recycled material manufacturer pays the product manufacturer a defined price to "store" its material in a product (up to €300/Mg). This practice is not uncommon in Germany.

The chemical industry in Germany is in a difficult position because its fossil fuel-based business model is no longer profitable. Therefore, phasing out petroleum and natural gas would be a way out. This would require a transition to other carbon sources, also in order to achieve greater resilience. And for climate protection reasons, this transition would be necessary in any case (defossilization). The carbon that is currently being downcycled does not contribute to the defossilization of the chemical industry; in fact, it is a waste of carbon.

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published: Innsbruck Waste and Resources Day 2026, 2|2026
Keywords: Material Recovery, Pollution Control, Sustainability, Climate, Resource management, Plastics, Methods, Analyses, Data, Awareness - Training