Scrap - an infinite resource?
Examining recycling myths and resource scarcity
In the discussion about sustainable materials and the circular economy, aluminium scrap is often heralded as the gold of the 21st century. While global demand for aluminium is rising sharply - with forecasts predicting current levels to double by 2050 [1] - there are pressing issues to resolve. Can we rely on recycling to satisfy the world’s hunger for aluminium? Or are we on course to lose our valuable resources to the highest bidders from overseas? The following article casts a light on the situation and explains why an urgent rethink is needed.
Aluminium demand: A growing challenge
At present, recycled aluminium covers just a third of the world’s total aluminium consumption. Even if this figure rises to 50% in future, the world will still be dependent on primary aluminium, despite the fact that 75% of all the aluminium ever produced remains in circulation. It often takes decades for aluminium products, such as buildings and cars, to reach the end of their life cycle and be recycled. This prolonged cycle also means that the volume of aluminium available for recycling remains limited, while demand is steadily rising. So, the current state of the scrap cycle means that aluminium recycling alone is not sufficient to satisfy demand.
If every customer were to demand a guaranteed recycling rate of 80%, we would be unable to meet this demand. We can only guarantee recycled material levels for specific products and volumes. Although we offer flexible solutions for smaller order volumes, larger orders often face significant issues regarding the availability of secondary material.
Aluminium scrap is obviously a prized commodity. This situation is further exacerbated by the fact that these limited quantities of scrap are increasingly exported to regions outside of Europe. The export of aluminium scrap and used products, such as cars, is removing this valuable material from the European market. In 2021 alone, Germany exported 2.5 million used cars while just 400,000 were sent for domestic recycling. [2] This loss of scrap demonstrates that the European aluminium industry must strive to efficiently close material cycles in order to remain competitive. This is particularly pertinent in Europe, where political initiatives such as the European Green Deal and efforts to establish a “circular economy” call for even more recycling, while increased a soaring demand is making raw materials more expensive. It is becoming increasingly difficult to secure sufficient quantities of scrap at competitive prices, which in turn drives up the price of finished products.
Scrap separation and sorting: A complex task with a misconception of costs
A widespread misconception is that recycled aluminium is necessarily more economical than primary aluminium. Although the energy involved in recycling aluminium is just 5% of that required to produce primary aluminium, the overall cost structure is far more complex and is influenced to a significant extent by the quality and composition of available material streams. In practice, a distinction is made between mixed scrap, which is the result of collected used metals, and almost pure scrap, which is a direct result of product manufacturing. These two categories require fundamentally different processing.There are two main techniques: mechanical processing and thermal processing. Mechanical processing starts by reducing the recycled material into smaller materials to produce different metal fractions that are suitable for subsequent sorting processes. The process of breaking materials down can involve several steps using a range of plant and machinery. Mixed scrap, which often contains numerous impurities, sometimes requires pre-sorting steps to remove objects that cannot be processed. The processed material must be reduced to a standardized grain size to prepare it effectively for fully automated sorting processes.
The difference between pre-consumer and post-consumer scrap is entirely superfluous, as no European manufacturer would ever conceive of generating more production waste just to increase their recycling rate. The decisive task is ensuring that aluminium scrap is retained in the European material cycle wherever possible and made reusable for the original product (alloy-to-alloy) wherever possible through adequate separation and processing.
The sorting that follows is a complex step and covers an entire spectrum of different processes. It ranges from separating light and heavy metals to isolating light metal alloys with a significant heavy metal content to sorting specific alloys within a given alloy family. Technical solutions to this challenge draw on the materials’ physical and chemical properties. The different densities of metals are used to separate light and heavy metals, while chemical composition is a decisive factor in sorting different light metals.This relies on highly sophisticated technologies, ranging from X-ray sensors used to determine metal densities to laser technologies used for chemical analysis. There have been impressive strides forward in separation and sorting technologies in recent years. For instance, sensor-based X-ray transmission sorting technology is now close to becoming standard practice in recycling companies that separate materials. This technique makes it possible to achieve high sorting quality, which means the resulting materials are suitable for use in cast and wrought alloys.One of the most advanced sorting methods is laser-induced breakdown spectroscopy (LIBS), a cost-effective method of sorting scrap into different alloys. However, despite these advances, there is still scope for improvement in terms of throughput and ablation, i.e. removing impurities such as paints and coatings from the surface of metals. This is a decisive factor in creating optimal conditions for chemical composition analyses while simultaneously ensuring high sorting quality.
Another aspect that adds to the complexity of scrap processing is the interactions of different recycling technologies and different scrap qualities. The quality and composition of collected scrap can vary significantly, which leads to laborious sorting and purification processes. These measures are necessary to ensure compliance with the purity standards and specific alloy characteristics required by the customer. The more laborious the cleaning, separation and sorting processes, the higher the costs involved in producing higher-quality metal fractions from scrap.
In some cases, the processing needed can be so extensive that, although technical feasible, it is no longer financially viable. So, the recycled materials are of higher quality, but have no reasonable relation to the expended financial and material resources. In reality, it often proves impossible to effectively separate certain fractions, such as plated material, including in car radiators and heat exchanges, or joints involving mixed materials. As a result, unwanted tramp elements are included in scrap fractions, which can negatively impact the quality of the final product.
Recycling-friendly alloy design: A necessity
Another widespread misconception is that all kinds of scrap aluminium can be used to produce all alloys. In reality, different aluminium alloys have exceptionally specific requirements. Alloys differ in terms of their mechanical properties, corrosion resistance and other characteristics achieved through precise compositions.Not every type of scrap can be used for every alloy because impurities and incompatible elements can negatively impact the quality and performance of the new alloy. This calls for a targeted approach when selecting and processing scrap to ensure that the final alloy has the desired properties.The automotive industry - which consumed around 18 million tons of aluminium worldwide in 2020 [3] - is just one example of the challenges of recycling-friendly design. Motor vehicles are made up of complex alloys that are subject to stringent requirements in terms of strength and corrosion resistance. Recycling these alloys requires precise sorting techniques and special processes to achieve the desired material properties. This is precisely why the concept of recycling-friendly alloy design is gaining traction. It promotes the development of new alloys and products with the aim of optimizing recycling processes. This means that the end-of-life recycling efficiency of aluminium products is taken into account in their design and production.Designs following this approach minimize the risk of impurities and make it easier to sort and reuse scrap, which ultimately leads to more sustainable and more cost-efficient production. It is also important to scrutinize defined specifications. Ultimately, these specifications date back to a time in which material properties were defined using primary alloys, i.e. based on the highest possible figures for a given property.These figures are often transposed without checking whether they are genuinely necessary. A differentiated approach to existing specifications and cautious adaptation to reflect actual requirements can promote the use of recycled alloys and, consequently, tramp elements.
Conclusion
In the context of rising demand for aluminium, limited availability of scrap and complex processing requirements, the industry must rethink its approach. The assumption that recycling is always more cost-efficient than primary production is misleading. Seizing the potential benefits of recycling will require innovative approaches, including recycling-friendly alloy design. It is only through targeted measures to optimize material use that we will be able to overcome the challenges of the circular economy and ensure a sustainable supply of aluminium for the future.
References:
[1] European Aluminium (01.03.2019) „Vision 2050. Der Beitrag von European Aluminium zum EU-Fahrplan für eine kohlenstoffarme Wirtschaft bis 2050“, S. 3[2] Umweltbundesamt (11.03.2024) Altfahrzeugverwertung und Fahrzeugverbleib, in Umweltbundesamt. Zugriff am 3. Oktober 2024 von Altfahrzeugverwertung und Fahrzeugverbleib | Umweltbundesamt [3] WVM. (8. Oktober, 2019). Verwendete Menge an Aluminium in Deutschland nach Hauptverwendungsgebieten im Jahr 2018* (in 1.000 Tonnen) [Graph]. In Statista. Zugriff am 03. Oktober 2024, von https://de.statista.com/statistik/daten/studie/28203/umfrage/verwendung-von-aluminium-nach-industriezweigen-in-2007/
