Across Europe, industrial clusters remain essential to economic stability, employment and technological progress. Yet they also represent some of the most resource-intensive and environmentally challenging parts of the economy. Built over decades to maximise production, these regions were not designed with circularity in mind. As a result, waste streams, unused (energy) resources and emissions continue to be treated as by-products rather than opportunities.
The IS2H4C project positions itself directly within this tension. It seeks to progressively transform how these regions operate by transforming them into Hubs for Circularity.
From linear industry to circular systems
At the heart of IS2H4C lies the concept of industrial symbiosis. This approach encourages collaboration between traditionally separate industrial actors, allowing them to exchange energy, materials, water and services in ways that reduce waste and improve efficiency.
While this idea is not new, its implementation has so far remained limited in scale. IS2H4C aims to move beyond isolated exchanges and instead develop integrated systems where industrial zones function as interconnected ecosystems.
In this model, waste heat from one facility can supply nearby buildings, captured carbon can become a feedstock for chemicals / e-fuels production, and renewable energy can be shared across industrial processes. These interactions are not only physical but increasingly digital due to the need for information-based symbiosis, supported by platform-based solutions for real-time resource tracking and operations.
The intention is to reduce resource consumption, emissions and dependency on virgin materials through coordinated, system-level optimisation.
Demonstrating circularity in practice
A defining feature of IS2H4C is its focus on real-world implementation. The project brings together four demonstration hubs located in the Netherlands, Germany, Spain and Türkiye. Each hub represents a distinct industrial landscape, with different resource flows, infrastructures and transition challenges, allowing the project to test circularity under varied conditions.
The Dutch Hub develops a regional hydrogen-based circular energy system linking industry with urban and public infrastructure. At its core is the production of green hydrogen via electrolysis, powered by renewable energy sources. The hub demonstrates multiple synergies, including oxygen reuse in wastewater treatment, water recycling back to electrolysis, and hydrogen distribution for local energy applications (e.g., replacing natural gas). It represents a transition from industrial symbiosis toward a multi-actor, regionally embedded Hub for Circularity integrating energy, water, and infrastructure systems.
The German Hub centres on carbon capture and utilisation (CCU) within an industrial setting. Its main activity is the capture of CO₂ emissions and their transformation into value-added products such as e-methanol (or equivalent alternatives where needed). While implementation pathways have evolved, the hub continues to demonstrate how captured carbon can re-enter industrial value chains, supporting decarbonization and circular resource flows. It highlights the importance of technological flexibility and industrial feasibility in scaling circular solutions.
The Basque Hub focuses on heavy industry integration and carbon management. It connects sectors such as steel, oil refining, pulp and paper, and lime production to demonstrate how industrial symbiosis can reduce emissions and resource use. Key activities include the oxycombustion, capture and utilisation of CO₂, its conversion into e-fuels (e.g., e-methane), and the valorisation of industrial by-products such as steel slags for construction materials. The hub illustrates how tightly coupled industrial clusters can evolve into circular systems through shared infrastructures and cross-sector synergies.
The Turkish Hub focuses on the production of Non-Isocyanate Polyurethanes (NIPU) from captured CO₂ emissions originating from a refinery, demonstrating a direct carbon utilisation pathway within an industrial symbiosis setting. These circular materials are then applied in refrigerator manufacturing, replacing conventional polyurethane used in insulation. By linking captured carbon to end-product manufacturing, the hub showcases how innovative materials can enable low-carbon, circular production in large-scale industrial value chains.
Across all four hubs, the approach remains consistent. Rather than replacing established systems, the project builds on existing infrastructure and industrial relationships. This reflects a transition-oriented approach where circularity is achieved by reconfiguring and connecting existing assets into more efficient and integrated systems.
Towards a European model for circular hubs
The broader ambition of IS2H4C is to establish a replicable model for circular industrial development, supporting Europe’s transition towards climate neutrality.
This effort is driven by a multidisciplinary consortium of industrial partners, research organisations, universities and technology providers. Each contributes a specific role, from real-world implementation and technological development to analysis, policy alignment and stakeholder engagement. This reflects the cross-cutting nature of the transition.
The project itself operates through coordinated collaboration across sectors. Just as industrial symbiosis depends on collaboration between companies, IS2H4C relies on coordinated action across sectors to deliver meaningful change.
Hubs for Circularity thus act as platforms where industry, research, policymakers and communities come together to align efforts and develop transferable solutions.
A transition still in progress
IS2H4C represents an ongoing effort to bridge the gap between ambition and implementation. It operates in a space where technological capability is advancing rapidly, but systemic change remains complex and uncertain.
IS2H4C does not assume a fixed end-state. Instead, it highlights the conditions required to make it viable at scale. It contributes to a structured transition pathway for industrial regions, building on existing strengths while addressing current inefficiencies.
Whether this approach can be replicated widely will depend on how effectively these systems can be scaled, financed and governed in the years ahead.
To learn more about IS2H4C, follow our progress, engage with ongoing activities and explore how industrial regions are evolving towards circularity, connect with us on LinkedIn and Bluesky or visit our website at www.is2h4c-project.eu.
