Investigation of Carbon Capture Technologies in Cement Manufacturing

Investigation of Carbon Capture Technologies in Cement Manufacturing
Abstract
The cement industry is responsible for approximately 7–8% of global anthropogenic CO₂ emissions, with roughly half originating from the calcination of limestone—an unavoidable process emission. Carbon capture technologies are widely regarded as the essential "backstop" solution for achieving carbon neutrality in this hard-to-abate sector. This report investigates the principal carbon capture pathways under development and deployment in cement manufacturing: post-combustion capture (amine absorption, membranes, cryogenic separation), oxy-fuel combustion (partial and full), calcium looping, and direct separation (indirect calcination). The technical principles, energy penalties, capture efficiencies, and demonstration project status of each technology are examined. Comparative analysis reveals that calcium looping and oxy-fuel combustion offer favorable integration with existing cement kiln processes, while cryogenic separation demonstrates competitive energy performance (1.19–1.21 MJₑₗ/kgCO₂). Key challenges include high energy penalties, capital costs, and the need for CO₂ transport and storage infrastructure. The report concludes that a portfolio of capture technologies, tailored to plant-specific conditions and regional infrastructure, will be necessary for industry-wide decarbonization.
Keywords: Carbon capture; Cement decarbonization; Oxy-fuel combustion; Calcium looping; Post-combustion capture; CCUS
1 Introduction
Cement production is inherently carbon-intensive due to the calcination of limestone, which releases CO₂ as an unavoidable by-product of the chemical reaction. Approximately 0.5–0.7 kg of CO₂ is produced per kg of cement, with process emissions from calcination accounting for about half of the total, the remainder arising from fuel combustion. Unlike sectors where emissions originate predominantly from energy use, the cement industry cannot eliminate process emissions through fuel switching or energy efficiency alone. This makes carbon capture the critical "backstop" technology for achieving deep decarbonization.
The cement industry has committed to ambitious decarbonization targets, with major producers aiming for carbon neutrality by 2050. The International Energy Agency (IEA) has identified carbon capture, utilization, and storage (CCUS) as crucial for assisting the global effort to attain net-zero emissions by 2050, with the cement industry being a key application area. However, widespread deployment faces significant technical, economic, and infrastructural barriers.
This report investigates the principal carbon capture technologies applicable to cement manufacturing, examining their technical principles, performance characteristics, energy requirements, and deployment status. The analysis focuses on technologies that have progressed beyond laboratory scale to pilot or demonstration projects, providing insights into the practical challenges and opportunities for industrial-scale implementation.
2 Classification of Carbon Capture Technologies for Cement
Carbon capture technologies for cement can be broadly categorized into four principal pathways based on where and how CO₂ separation occurs: post-combustion capture, oxy-fuel combustion, calcium looping (a form of post-combustion capture using high-temperature solid sorbents), and direct separation (indirect calcination). Each pathway offers distinct advantages and faces unique challenges when integrated with cement kiln systems.
2.1 Post-Combustion Capture
Post-combustion capture involves separating CO₂ from the flue gas after fuel combustion and calcination have occurred. This is an "end-of-pipe" approach that does not require fundamental changes to the cement production process. The principal methods under development include amine absorption, membrane separation, and cryogenic separation.
Amine Absorption. The most mature post-combustion technology, amine absorption uses chemical solvents (typically monoethanolamine, MEA) to selectively absorb CO₂ from flue gas. The solvent is subsequently regenerated by heating, releasing a concentrated CO₂ stream for storage or utilization. This technology is commercially deployed in other sectors but faces significant energy penalties when adapted to cement flue gas, which contains high dust loads and trace contaminants. The IEA notes that capturing CO₂ from processes with dilute gas streams such as cement production can incur costs ranging from USD 40 to 120 per tonne of CO₂ captured due to the impact on the energy balance.
Membrane Separation. Membrane technologies use selective permeability of polymer or inorganic materials to separate CO₂ from other flue gas components. A significant recent development is the membrane pilot plant developed by Helmholtz-Zentrum Hereon and commissioned at Holcim Germany's cement works in Höver. The facility is designed to capture up to 90% of the plant's CO₂ emissions, expected to capture up to 10,000 tonnes of greenhouse gases annually at this stage of expansion. Membranes offer advantages in compactness and modularity, though industrial-scale validation remains limited.
Cryogenic Separation. Cryogenic capture separates CO₂ by cooling flue gas to temperatures at which CO₂ condenses or solidifies, enabling high-purity separation. Recent techno-economic analysis indicates that cryogenic capture achieves an energy penalty of 1.19 MJₑₗ/kgCO₂ at 90% capture, significantly lower than conventional MEA-based capture. Increasing capture to 95% maintains nearly constant energy penalty (1.19–1.21 MJₑₗ/kgCO₂). The cost of avoided CO₂ is estimated at approximately €127/tCO₂. A notable European milestone is the CryoCEM project in Austria, designed to recover up to 30,000 tCO₂/year with commissioning targeted for 2026.
2.2 Oxy-Fuel Combustion
Oxy-fuel combustion replaces air with oxygen for fuel combustion, producing a flue gas stream consisting primarily of CO₂ and water vapor, which can be easily separated to yield a high-purity CO₂ stream. This approach fundamentally alters the combustion environment within the kiln and calciner.
Partial Oxy-Fuel Combustion. In partial oxy-fuel configuration, only the calciner is fired with oxygen, while the rotary kiln continues to operate with air. This limits the maximum CO₂ capture rate to 70–80% but avoids modifications to kiln temperature profiles and minimizes issues related to air in-leakage. A key technical challenge is that the decomposition kinetics of raw meal constituents are inhibited under elevated CO₂ partial pressures. The decomposition temperature of calcium carbonate increases by 60–70°C under oxy-fuel atmosphere, requiring higher calciner temperatures to achieve adequate calcination rates.
Full Oxy-Fuel Combustion. Full oxy-fuel combustion extends oxygen firing to both the calciner and rotary kiln, enabling capture rates of 90–95%. First-generation systems use flue gas recirculation to control combustion temperature. Research has demonstrated that oxy-fuel atmosphere has no significant effect on clinker quality, and kiln temperature distribution can be maintained comparable to air combustion through parameter adjustment. Second-generation systems eliminate flue gas recirculation, controlling kiln temperature through excess O₂, which has shown ideal temperature control effects.
China has conducted industrial-scale experimental investigations based on a 200,000 tonne/year CO₂ capture demonstration project incorporating oxy-fuel calciner technology. The research systematically examined changes in fuel combustion, raw meal calcination, and clinker sintering under N₂/O₂ and CO₂/O₂ atmospheres, comparing flue gas composition, temperature, pressure, and raw meal calcination rates.