Tackling climate change requires not only ambitious targets but also the rapid development and deployment of practical decarbonization solutions. Among the available strategies, Carbon Capture and Utilization (CCU) has emerged as a promising pathway, enabling the transformation of waste CO₂ into valuable chemicals and fuels. This approach is especially relevant for hard‑to‑abate sectors including cement manufacturing, where a significant fraction of emissions is inherently linked to the production process and cannot be eliminated through electrification or energy efficiency measures alone.

In this context, the present work presents the design, experimental validation, and integration of an electrochemical CO₂ recycling demonstration plant tailored for cement plant flue gases. The study addresses two stages of the CCU value chain: the capture of CO₂ from industrial exhaust streams and its subsequent electrochemical conversion into formate [1, 2].

First, CO₂ capture is achieved using a membrane‑based separation system built around polymeric hollow‑fiber modules. This technology is well-suited for post‑combustion applications due to its modularity, low energy demand, and operational simplicity [3]. Experimental results show that, when treating flue gases containing 7–15% v/v CO₂, a single membrane stage increases the CO₂ concentration to approximately 18.5%. However, achieving the higher purities required for efficient downstream conversion demands a multistage configuration. Guided by predictive modelling, a three‑stage membrane reaches CO₂ concentrations above 95%, providing feed for electrochemical utilization.

The captured CO₂ is then converted into formate in a laboratory‑scale electrochemical reactor with an active area of 100 cm². The system operates using a gas diffusion electrode (GDE) based on (BiO)₂CO₃, selected for its high selectivity and improved stability under reaction conditions [4]. Long‑term operation tests, over 12 consecutive days, demonstrate system robustness. The Faradaic efficiency for formate production is initially close to 100% and gradually decreases to approximately 75% due to electrode degradation. Importantly, by-product formation remains limited, with hydrogen and carbon monoxide efficiencies consistently below 10% and 4%, respectively. Overall, the system achieves cumulative formate production exceeding 20 mol, with a stable daily output of around 1.7 mol.

To support the transition from laboratory‑scale experiments to industrial implementation, the experimental data obtained from both the capture and conversion units are used to develop predictive models. These models are integrated into a digital twin predicting key process variables, including CO₂ concentration, formate production, and system efficiency, with coefficients of determination close to 0.99. This digital framework enables real‑time monitoring, predictive control, and process optimization, enhancing the reliability and scalability of the system.

Building on these results, an integrated pilot plant is proposed, designed to process up to 20 L·min⁻¹ of captured CO₂ with an electrochemical active area of 1000 cm². The process includes flue gas conditioning, multistage membrane separation, gas compression, and direct coupling with the electrochemical reactor. Despite the promising results, several challenges remain for industrial deployment, including improving long‑term electrode durability, reducing energy consumption, and optimizing the management of unconverted CO₂ and recycled process streams.

Overall, this study demonstrates that the integration of membrane‑based CO₂ capture and electrochemical conversion is a technically viable and scalable solution for cement plant emissions. By combining experimental validation with digital twin modelling, this work provides a solid engineering foundation for advancing CCU technologies as a realistic route toward decarbonizing heavy industry and supporting the transition to more sustainable manufacturing systems.