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The ceramic industry is increasingly positioned at the forefront of the transition toward a circular economy, where raw material sourcing is being fundamentally redefined. Rather than relying exclusively on virgin mineral resources, there is growing evidence that both biogenic and industrial waste streams can be transformed into functional components of ceramic formulations. This transition goes beyond simple substitution; it requires the deliberate redesign of ceramic systems to accommodate variability in chemical composition, reactivity, and thermal behaviour. Within this framework, waste is no longer viewed as an end-of-life by-product, but as a resource whose value depends on how effectively it is characterised, processed, and integrated into manufacturing routes.

A representative example is the EGGSHELLENCE project, funded under the European LIFE programme, which explored the valorisation of eggshell waste as a bio-based calcium carbonate source for the ceramic industry. Developed through a consortium including the Institute of Ceramic Technology (ITC-AICE, Castellón, Spain), the University of Aveiro (DEMaC – Department of Materials and Ceramic Engineering and CICECO – Aveiro Institute of Materials, Portugal), and Portuguese and Spanish industrial partners, the project addressed a high-volume biogenic residue with significant untapped potential. Eggshell waste was processed into a purified CaCO₃ stream and evaluated as a partial replacement for conventional mineral carbonates. The results demonstrated the technical feasibility of this substitution and highlighted the importance of controlling key parameters such as particle size distribution, removal of organic residues, and thermal decomposition behaviour. These factors are critical to ensuring consistent performance during firing, demonstrating that even biologically derived waste can be engineered into reliable and industrially relevant secondary raw materials.

In parallel, the ECOGRÉS + NG project, co-financed under the Portugal 2020 framework, represents a complementary approach focused on industrial symbiosis. Led by GRESTEL, a Portuguese manufacturer of utilitarian stoneware, in collaboration with DEMAC/CICECO and several waste producers, the project investigated the incorporation of diverse industrial wastes into stoneware bodies. These included fly ashes from paper pulp production, aluminium anodisation sludges, and galvanisation by-products. Unlike single-stream approaches, this strategy required managing chemically diverse inputs, each contributing distinct functional roles within the ceramic matrix. The findings showed that high waste content formulations can achieve stable sintering behaviour, competitive mechanical properties, and even reduced firing temperatures. This demonstrates that waste streams can actively redefine processing windows, rather than serving merely as inert fillers. 

Building on these results, the ECOGRES initiative represents the industrial-scale implementation of the concepts developed in the ECOGRÉS + NG project. By translating laboratory-scale formulations into a dedicated production platform, it validates the scalability of circular ceramic systems under real manufacturing conditions. This includes addressing challenges such as variability in raw materials, continuous firing processes, and strict quality requirements. The progression from research to industrial deployment provides strong evidence that circular approaches can be both technically robust and economically viable.

https://www.lifeeggshellence.eu/en/home/

Maria Paula da Silva Seabra

Department of Materials and Ceramic Engineering (DEMaC), Aveiro Institute of Materials (CICECO), University of Aveiro, Portugal

pseabra@ua.pt