The decarbonisation challenge in hard-to-abate sectors

The beginning of 2026 marks the entry into force of the definitive phase of the Carbon Border Adjustment Mechanism (CBAM), which extends to imported goods the carbon pricing logic already underpinning the EU Emissions Trading System, still limited to the European context. This emissions management approach, particularly concerning greenhouse gas (GHG) emissions, highlights the importance for hard-to-abate sectors of identifying new solutions for decarbonisation. At the same time, within this framework, solutions that enhance the value of industrial waste by reusing it as a secondary raw material are becoming increasingly crucial.

Within this context, the CCS4CER project was launched: Carbon Capture, Storage and CO₂ Mineralisation for the Ceramic Industry, funded by European resources through the Emilia-Romagna Regional Programme (ERDF 2021–2027), Priority Axis 1 – Research, Innovation and Competitiveness, Action 1.1.2 (https://www.ccs4cer.it/). Now in its third year, CCS4CER is delivering concrete results both in the study of plant solutions for carbon capture and in the valorisation of one of the main industrial wastes currently characterising the ceramic sector and other energy-intensive industries: spent lime derived from bag filters used for flue gas deacidification during kiln firing processes.
The project, coordinated by the Centro Ceramico, benefits from the collaboration of highly specialised laboratories within the Emilia-Romagna High Technology Network, namely CIRI-FRAME (University of Bologna), LEAP (Politecnico di Milano) and Romagna Tech, as well as the involvement of companies from the ceramic district (Ascot Gruppo Ceramiche, Panariagroup Industrie Ceramiche S.p.A. and SACMI Cooperativa Meccanici Imola S.C.).

Initially, a sampling campaign was carried out on spent lime collected from several ceramic companies, followed by a comprehensive physico-chemical characterisation. The capacity of this waste to sequester CO₂ is correlated with the amount of unreacted Ca(OH)₂ in the sample, which varies depending on the acid gas abatement protocols used by different companies. The variability observed in the analysed samples indicates a relatively high CO₂ sequestration capacity, ranging between 190 and 390 grams of CO₂ per kilogram of waste.
The sampled materials, differing in composition, were used in CO₂ mineralisation tests in wet processes (solid–liquid–gas), carried out in both batch and semi-continuous modes at different scales.

During the study, various reaction conditions were explored by modifying operating pressure, gas flow and composition, suspension concentration and the specific type of waste used. Reaction profiles, obtained through continuous monitoring of CO₂ consumption over time, made it possible to study the kinetics of the process. The results show that the main factors influencing the efficiency of wet mineralisation of spent lime are the liquid-to-solid ratio, CO₂ flow rate and reaction time. The data also demonstrate that CO₂ removal from gas streams through mineralisation of this type of waste is highly efficient even under mild conditions (low temperature and pressure) and with diluted CO₂ concentrations.
Tests conducted so far indicate that mineralisation reduces the release of pollutants from spent lime, which, in the trials carried out, shifts from being classified as hazardous special waste to non-hazardous waste, with significant benefits even in terms of landfill disposal.

The reuse of mineralised spent lime in cementitious binders was also investigated, with the aim of transforming waste from one industrial sector into a resource for another. The cement industry has long been engaged in developing solutions to reduce clinker content and the environmental impact of its products. The mineralised material was tested both as a filler replacing natural limestone (in Portland-limestone cements) and as a component in a new class of low-impact cements based on limestone and calcined clay (LC3 – Limestone Calcined Clay Cement).
The test results show that the behaviour of the mineralised product in cement mortars is fully comparable to that of pure limestone, both in terms of mechanical performance and physico-chemical properties, and may even provide performance benefits in LC3-based mortars. It was also confirmed that the release of any heavy metals present in the original spent lime is reduced in the aqueous phase when used in cementitious systems.

In addition, CO₂ capture technologies for ceramic process flue gases were evaluated through simulations based on industrial data, considering a plant producing 10,000 m² of tiles per day (1 cm thickness). Without capture systems, the selected plant consumes 10.3 MW (LHV) of natural gas and emits 18 kt/year of CO₂.
Decarbonisation of the production process can be achieved through molten carbonate fuel cells (MCFC), which enable both CO₂ removal from flue gases and the generation of decarbonised electricity to power CO₂ compression systems. Operating at around 600°C, MCFCs can be integrated into the process, improving energy efficiency while increasing plant complexity.
The performance of fuel cells was compared with chemical absorption processes based on amine solvents and with process electrification, which replaces natural gas combustion. The techno-economic analysis shows that solvent-based systems achieve up to 90% CO₂ capture but present the highest decarbonisation costs due to unfavourable scale factors. MCFC systems reduce CO₂ emissions by 84% and lower natural gas consumption to 9.4 MW (LHV). Electrification achieves up to 94% decarbonisation, leaving only process-related CO₂ emissions from firing, but requires significant plant modifications and the use of 11.3 MWel.
Both solutions increase the cost of ceramic tiles by €0.7–1.2 per m², corresponding to a production cost increase of between 8% and 22%, depending on product quality and energy prices.

R. Pascolo, E. Franzoni - Centro Ceramico, Sassuolo, Modena;
M.C. Bignozzi - Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali, Bologna;
A. Catalano, A. Allegri, S. Albonetti - CIRI-FRAME, University of Bologna, Dipartimento di Chimica Industriale, Bologna.
R. Scaccabarozzi - LEAP, Laboratorio Energia e Ambiente Piacenza; 
L. Cretarola - Politecnico di Milano, Dipartimento di Energia, Milano