Salt slag remains one of the most difficult issues for aluminium recyclers to manage today, says Dr Zhongping Que

The image used in this article is generated with an AI tool and does not depict any real-time moment

Europe’s aluminium recycling industry is facing a difficult question: how can increasingly mixed and contaminated scrap be transformed into high-quality alloys without adding more waste, emissions or processing costs? This is what has been addressed by Dr Zhongping Que, an expert in advanced metallurgy and sustainable aluminium recycling, in this interview. She has explained how the CLEANMAT project has brought a viable solution to this through smarter sorting, intelligent pre-treatment, advanced refining and closer control of scrap quality before melting. Her work focuses on alloy design, impurity management and recycling technologies that support a low-carbon, circular metals industry.

The discussion explores how next-generation recycling strategies could improve scrap quality, reduce flux consumption and retain more material value within Europe. It also examines the commercial realities of high-value recycling, the limits of conventional processing and the importance of collaboration between researchers, technology providers and industrial partners.

Read the full interview to understand why the next breakthrough in aluminium recycling may begin long before the scrap reaches the furnace.

AL Circle: CLEANMAT targets up to 97 per cent reduction in flux use without compromising alloy quality or yield. What makes this target technically achievable? What was the core industry problem that led to the creation of the CLEANMAT project?

Dr Zhongping Que:  The target of reducing flux use by up to 97 per cent is based on integrating several complementary innovations across the aluminium recycling process, rather than relying on a single technological advance. By improving the quality and consistency of recycled feedstock and optimising recycling operations, CLEANMAT aims to significantly reduce the need for chemical flux while maintaining alloy quality and production efficiency.

The project was established to address a major challenge facing the aluminium industry: the growing volume of mixed and contaminated end-of-life scrap. As recycled aluminium becomes increasingly important for achieving climate and circular economy goals, manufacturers need new solutions that can produce high-quality alloys from more complex scrap streams without increasing energy consumption, waste generation, or reliance on primary aluminium.

CLEANMAT brings together expertise from across Europe to develop innovative recycling technologies that improve resource efficiency, reduce environmental impact, and support a more sustainable and competitive aluminium industry.

AL Circle: Recycling Europe mentions emissions such as particulates, VOCs, dioxins and salt slag waste. Which of these is the most difficult for aluminium recyclers to control today? How serious is the problem of turning mixed and contaminated scrap into high-quality aluminium alloys at a commercial scale?

Dr Zhongping Que: Among these challenges, salt slag remains one of the most difficult issues for aluminium recyclers to manage today. It is closely linked to the melting process and the use of salt fluxes, which help improve metal recovery but also generate residues that require further treatment, recycling, or disposal. This creates additional economic and environmental challenges, particularly as regulations around waste management continue to become stricter.

Particulates, VOCs, and dioxins are also important concerns, especially when recycling scrap containing coatings, oils, and other contaminants. However, these emissions can generally be managed through established gas treatment and filtration technologies. The more fundamental challenge is controlling the quality of recycled aluminium at the point where increasingly complex scrap streams enter the process.

As the industry moves towards greater use of end-of-life scrap, recyclers face the challenge of converting mixed and contaminated materials into consistent, high-quality aluminium alloys on a commercial scale. Variations in alloy composition, surface treatments, and impurities make it difficult to achieve the required quality while maintaining high recovery rates and low environmental impact. The future of aluminium recycling depends on improving the ability to handle complex scrap streams efficiently, enabling higher-value recycling with reduced reliance on additional processing and primary aluminium.

Read all the latest developments in Europe’s aluminium recycling industry: Click here

AL Circle: Can CLEANMAT help Europe keep more scrap value, cut recycling emissions and build a stronger circular aluminium supply chain? Through this project, what should change in Europe’s aluminium recycling industry in the coming years?

Dr Zhongping Que: Yes. CLEANMAT aims to contribute to three important goals for Europe’s aluminium industry: retaining more value from scrap, reducing the environmental impact of recycling, and strengthening a more resilient circular aluminium supply chain.

Today, one of the biggest challenges is that increasing amounts of end-of-life aluminium scrap are becoming more complex and difficult to process. When scrap quality is inconsistent, valuable aluminium resources can be lost through downcycling, additional processing requirements, or reduced alloy performance. CLEANMAT addresses this challenge by supporting more efficient recycling approaches that enable better utilisation of secondary aluminium resources.

Reducing emissions is another key priority. By improving the efficiency of recycling processes and reducing the need for energy-intensive treatments and additional inputs, the project can contribute to lowering the environmental footprint of secondary aluminium production.

Looking ahead, Europe’s aluminium recycling industry will need to move towards a more advanced and integrated circular model, where scrap is recognised as a valuable resource rather than simply a waste stream. This will require closer collaboration across the value chain, combining improved recycling technologies, better material management, and stronger links between recyclers and alloy producers.

Ultimately, CLEANMAT aims to support a future where more aluminium remains within Europe’s circular economy, improving both environmental performance and industrial competitiveness.

AL Circle: Why is this project important for Europe’s circular aluminium economy at this point in time? How will AI-driven multi-sensor characterisation improve the identification of contaminants in aluminium scrap?

Dr Zhongping Que: This project is particularly important for Europe’s circular aluminium economy because the industry is facing a combination of challenges: growing volumes of end-of-life scrap, increasingly complex material streams, and the need to significantly reduce carbon emissions. As Europe moves towards a more circular economy, maximising the value of recycled aluminium will be essential to reduce dependence on primary aluminium production while maintaining industrial competitiveness.

One of the main barriers is that modern aluminium scrap is becoming more diverse and difficult to manage. Different alloys, surface treatments, and contaminants can be mixed together, making it challenging to produce consistent high-quality recycled aluminium.

AI-driven multi-sensor characterisation offers a new approach by combining information from different detection technologies and using advanced data analysis to better understand the composition and quality of scrap materials. This enables more accurate identification of materials and contaminants compared with traditional approaches, helping recyclers make better decisions about how scrap should be processed.

In the future, such technologies will help transform aluminium recycling into a more intelligent and efficient system, where more complex scrap streams can be converted into high-value secondary aluminium products. This will support Europe’s goals of reducing emissions, improving resource efficiency, and building a stronger circular aluminium supply chain.

AL Circle: CLEANMAT combines digital sorting, intelligent pre-treatment and advanced melt refining. Which part of the process is expected to deliver the biggest technical breakthrough? What types of residual contaminants are the most problematic for aluminium recyclers today?

Dr Zhongping Que: CLEANMAT combines several innovations across the aluminium recycling process, and the key breakthrough is expected to come from better integration between these different stages. Improving the understanding and control of scrap quality before melting is particularly important, because it can help recyclers manage increasingly complex material streams more effectively and reduce the need for intensive corrective treatments later in the process.

Advanced sorting, pre-treatment, and improved melt refining each play an important role. Together, they aim to increase the consistency of recycled aluminium, improve recovery rates, and support the production of higher-quality secondary alloys.

For aluminium recyclers today, some of the most challenging contaminants are alloying elements that become difficult to control when present in mixed scrap streams, such as iron, copper, and zinc, as well as non-metallic contaminants including coatings, oils, plastics, and oxides. These materials can affect alloy performance, increase processing requirements, and contribute to waste generation during recycling.

The challenge is not only removing individual contaminants, but managing the increasing complexity and variability of modern scrap. Developing more intelligent and efficient ways to handle these materials is therefore essential for enabling higher-value aluminium recycling in Europe.

AL Circle: How does this project respond to the growing concern that valuable aluminium scrap is being exported or downcycled instead of being reused in high-value European applications? 

Dr Zhongping Que: This is a critical issue for Europe’s circular aluminium economy. As demand for low-carbon materials increases, retaining more aluminium scrap within Europe and maintaining its value through recycling will become increasingly important.

One of the main reasons valuable scrap can be exported or downcycled is the difficulty of consistently achieving the quality required for high-value applications. Complex scrap streams often contain a mixture of alloys and contaminants, making it challenging for recyclers to produce reliable secondary aluminium with the required properties.

CLEANMAT addresses this challenge by supporting more advanced approaches to scrap management and recycling, helping improve the quality, consistency, and utilisation of recycled aluminium resources. By enabling better processing of complex scrap streams, the project aims to increase the amount of aluminium that can be recycled into higher-value applications rather than being lost through downcycling.

In the longer term, initiatives such as CLEANMAT can contribute to a stronger European circular aluminium supply chain, where more material value is retained within Europe, reducing resource dependency and supporting the transition towards a low-carbon metals industry.

AL Circle: How will the life-cycle assessment measure the real emissions benefit of CLEANMAT compared with conventional aluminium recycling?

Dr Zhongping Que:  The life-cycle assessment (LCA) in CLEANMAT will provide a comprehensive evaluation of the environmental benefits of the project by comparing its recycling approach with conventional aluminium recycling routes.

The assessment will consider the full recycling value chain, including material preparation, processing, and the production of recycled aluminium alloys. Key indicators such as greenhouse gas emissions, energy consumption, resource efficiency, and waste generation will be analysed to understand the overall environmental performance.

A key objective of the LCA is to identify where improvements in the recycling process can deliver the greatest environmental benefits. By enabling more efficient use of scrap resources and reducing the need for additional processing, CLEANMAT aims to lower the overall carbon footprint of secondary aluminium production.

Importantly, the assessment will be based on realistic industrial data and performance measurements, ensuring that the results reflect practical applications rather than only theoretical potential. This will help demonstrate how advanced recycling approaches can contribute to a more sustainable and circular aluminium industry in Europe.

AL Circle: How are universities, associations, and recycling companies collaborating with CLEANMAT? Could you brief us about their individual roles in the project?

Dr Zhongping Que:  CLEANMAT brings together 17 partners from across Europe, representing a wide range of expertise and sectors, including universities, research organisations, recycling companies, technology providers, industry associations, and policy stakeholders. This diverse partnership is essential because improving aluminium circularity requires solutions that address the entire value chain, from material understanding and technology development to industrial implementation and policy alignment.

Universities and research organisations provide fundamental scientific knowledge, advanced modelling, experimental validation, and expertise in areas such as material characterisation, recycling processes, and alloy performance. Their role is to develop the scientific basis needed for new recycling approaches and support knowledge transfer.

Technology providers contribute engineering expertise and help transform research concepts into practical solutions that can operate under industrial conditions. Their involvement is critical for developing and integrating advanced technologies that improve recycling efficiency and reliability.

Recycling companies bring real industrial experience, including access to complex scrap streams, operational knowledge, and pilot or industrial validation environments. They ensure that the innovations developed within CLEANMAT address real challenges faced by the recycling sector and are suitable for future commercial adoption.

Industry associations provide links to the wider aluminium value chain, supporting communication, stakeholder engagement, and the dissemination of project outcomes. They help ensure that the results are relevant to the broader sector and can support wider industry transformation.

Policy and sustainability stakeholders contribute knowledge of European strategies, regulatory priorities, and circular economy objectives. Their involvement helps ensure that CLEANMAT’s outcomes are aligned with Europe’s ambitions for resource efficiency, industrial competitiveness, and decarbonisation.

The strength of CLEANMAT comes from bringing these different perspectives together. By connecting scientific research, industrial expertise, technology development, and policy needs, the project aims to accelerate the transition towards a more sustainable, resilient, and circular aluminium industry in Europe.