What steel and cement symbiosis reveals about waste classification, cross-border shipments, and the case for common standards
The same steel slag can be considered a resource in one European country and waste in another. The material itself has not changed, nor has its chemical composition. Its legal status, however, can differ. For industrial symbiosis, this distinction matters. When materials cross national borders, a transaction involving a secondary raw material may instead fall under the rules governing waste shipments, bringing additional administrative requirements, costs and uncertainty. Steel slag already has established applications in Europe, including as a substitute for virgin materials in cement and construction. thyssenkrupp Steel, for example, uses blast furnace slag as a by-product in cement production, where it replaces clinker and can significantly reduce associated carbon emissions (thyssenkrupp Steel, n.d.). Yet these established uses do not guarantee that the material will be treated consistently across European borders.
Same material, different legal status depending on where you are
For a material like steel slag, reuse options are well established; the barrier isn’t technical. Whether such a material counts as waste or as a resource often isn’t settled by its composition, but by which country’s national authority is assessing it.
The application of waste, by-product, and end-of-waste rules at national level means that an identical material can be classified differently depending on where it is located. The Waste Framework Directive sets the conditions for this at EU level: Article 5 defines when a material qualifies as a by-product, and Article 6 sets out the criteria for end-of-waste status. Both provisions establish when a material stops being “waste”, but their implementation is left to individual member states. As a result, the same slag, with the same composition, can hold a different legal status depending on the country in question (Directive 2008/98/EC, Arts. 5 & 6; RISERS, “Making Waste Work: RISERS and the Future of EoW,” 2025).
Steel slag illustrates this well. Certain types of slag are treated as by-products in some EU member states and as waste in others (Loureiro et al., 2022, Sustainability). This divergence does not stop at national borders either. In countries such as Spain and Germany, the same material can carry different status from one region to another, according to industry sources. Crossing an international border adds a further layer of complexity on top of that.
Waste Shipment Regulation
The Waste Shipment Regulation addresses what happens when authorities in different countries take different views on a material’s classification. Under Article 29(1)–(2), classification depends on how the relevant Member States have implemented relevant articles of the Waste Framework Directive when determining whether an object or substance is waste, a by-product, or has ceased to be waste. Where the competent authorities of dispatch and destination cannot agree on whether an object or substance is waste or non-waste, it is treated as waste for the purpose of the shipment (Regulation (EU) 2024/1157, Art. 29).
That default has practical consequences. A waste classification can trigger the full notification-and-consent procedure, including prior notification to the authorities involved, a signed contract, a financial guarantee covering transport, recovery and up to 90 days of storage costs, and a response period of up to 30 days. These requirements do not apply when a shipment is classified as non-waste (Regulation (EU) 2024/1157, Arts. 5–9).
Disagreement between authorities can add another layer of complexity, since the operator may need to establish the material’s legal status under the relevant rules in both countries (Turunen, 2026). According to industry experts, some companies therefore plan shipment routes around Member States where classification is less likely to be contested, specifically to avoid triggering the waste default.
A shared technical basis would not change Article 29(2) default itself. It could make classification more consistent across countries, reducing the scope for disagreement between authorities. This is where standards can play a role.
How standards can help
Harmonized technical standards already provide a common basis for assessing secondary materials. EN standards for aggregates, including EN 12620, EN 13043, and EN 13242, specify technical requirements relevant to iron and steel-making slag used in construction (CEN, EN 12620; EN 13043; EN 13242). By providing common requirements for aspects such as composition, leaching behaviour and stability, they give authorities in different countries a shared technical reference when assessing end-of-waste status.
Standards do not determine the legal classification itself; Articles 5 and 6 of the Waste Framework Directive continue to govern that. Their role is to provide a technical basis that can be applied consistently across borders.
The CINDERELA project, funded under the EU Horizon programme, provides a concrete example of this approach. It developed a harmonized end-of-waste criteria protocol for secondary raw materials used as aggregates, with the aim of reducing country-by-country differences in end-of-waste implementation (CINDERELA, 2021).
RISERS’ own standardization work sits in this same space. Its fact sheets on BOF and EAF slag synergies, together with presentations to its Technical Committee, contribute to the development of a shared technical reference for the industry. Some industry voices, however, argue that existing national standards are already adequate and that further EU-level harmonization is unnecessary.
Standards can reduce differences in how authorities assess materials, but resolving the underlying legal divergence requires legislation. This is where the Circular Economy Act becomes relevant.
The role of Circular Economy Act
The Commission’s answer to this same divergence is expected later this year, in the form of the Circular Economy Act. A proposal is anticipated in the second half of 2026, though it hasn’t been published as of writing. The Commission’s stated aim is to establish a single EU market for secondary raw materials.
The Ellen MacArthur Foundation frames the underlying problem clearly: national rules currently differ enough that what counts as a “valuable resource” in one country can be classified as “waste” in another. The Circular Economy Act is meant to replace that patchwork with a more coherent rulebook (Ellen MacArthur Foundation, 2026).
Harmonization at EU level has failed before at this specific task. In 2013, the European Parliament rejected the Commission’s proposal for EU-wide end-of-waste criteria, that time for recovered paper (Turunen, 2026). This history makes the standards work described above relevant regardless of what the Circular Economy Act ultimately delivers.
Two levers, one goal
Neither lever works alone. Regulation can set the legal boundaries for what counts as waste, but it can’t resolve the day-to-day technical differences between authorities. Standards can narrow that gap, but they can’t replace the legal clarity that harmonized legislation provides. For industrial symbiosis to work across borders, regulation and standards need to move together.
Sources & further reading:
- thyssenkrupp Steel, “Blast furnace slags: From byproduct to valuable resource” (n.d.): https://www.thyssenkrupp-steel.com/en/company/sustainability/byproducts/using-blast-furnace-slags-sustainably.html
- RISERS Project, “Making Waste Work: RISERS and the Future of EoW” (2025): https://risers-project.eu/making-waste-work-risers-and-the-future-of-eow/
- Loureiro, C. D. A., Moura, C. F. N., Rodrigues, M., Martinho, F. C. G., Silva, H. M. R. D., & Oliveira, J. R. M. (2022). Steel Slag and Recycled Concrete Aggregates: Replacing Quarries to Supply Sustainable Materials for the Asphalt Paving Industry. Sustainability, 14(9), 5022. https://doi.org/10.3390/su14095022
- Regulation (EU) 2024/1157 of the European Parliament and of the Council of 11 April 2024 on shipments of waste, amending Regulations (EU) No 1257/2013 and (EU) 2020/1056 and repealing Regulation (EC) No 1013/2006. Official Journal of the European Union, L series, 30.4.2024.
https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32024R1157 - Turunen, Topi. (2026). “Waste by any other name? National end-of-waste rulings and waste shipments.” Review of European, Comparative & International Environmental Law. https://doi.org/10.1111/reel.70026
- RISERS Project, “Advancing Standardisation for Industrial Symbiosis in Ferrous Slags, Refractories and Steel Scrap: Insights from Survey and RISERS Working Group” (2025): https://risers-project.eu/advancing-standardisation-for-industrial-symbiosis-in-ferrous-slags-refractories-and-steel-scrap-insights-from-survey-and-risers-working-group/
- RISERS Project: https://risers-project.eu/
- Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives, Arts. 5 & 6. Official Journal of the European Union. https://eur-lex.europa.eu/eli/dir/2008/98/oj
- CEN. EN 12620: Aggregates for concrete.
- CEN. EN 13043: Aggregates for bituminous mixtures and surface treatments for roads, airfields and other trafficked areas.
- CEN. EN 13242: Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction.
- Ellen MacArthur Foundation. (2026). The EU Circular Economy Act: a critical opportunity. https://www.ellenmacarthurfoundation.org/eu-circular-economy-act
- CINDERELA project (Horizon 2020, grant agreement No. 776751) (2021). D5.5 – End of waste criteria protocol for waste used as aggregates https://www.cinderela.eu/The-project/Reports/D5.5-End-of-waste-criteria-protocol-for-waste-used-as-aggregates
