Towards a business case for CO2 mineralisation in the cement industry

Cement production contributes about 7% of anthropogenic CO2 emissions and has the highest carbon intensity per unit of revenue. With global cement demand projected to remain large, reducing embodied emissions is essential. Around 60% of cement’s emissions are process-inherent from limestone calcination, making them difficult to mitigate without process replacement or capture and permanent storage. While material substitution (e.g., wood) faces major adoption barriers and CCS adds costs, strategies that create revenue while reducing emissions are desirable. CO2 mineralisation, reacting CO2 with Mg- or Ca-rich silicate minerals or alkaline wastes to form stable carbonates, offers exothermic, long-term storage and potential product valorisation (e.g., as supplementary cementitious materials, SCM). Prior assessments often overlooked product value. The research question is under which conditions CO2 mineralisation integrated with cement production can yield a positive business case while delivering significant CO2e reductions. The study develops integrated techno-economic models for two mineral carbonation process routes to produce SCM for cement blending and evaluates performance under pessimistic, mid, and optimistic scenarios.

The paper reviews CO2 mineralisation pathways using natural Mg/Ca silicates (e.g., forsterite, lizardite, wollastonite) and alkaline industrial residues. Natural rocks are abundant and predictable but require mining with associated environmental impacts; industrial residues are regionally available but composition and costs may vary over time. Reported reactions are exothermic and store CO2 in stable carbonate minerals. Prior studies indicate net CO2 reductions of 0.44–1.17 tCO2e per tCO2 stored under current energy mixes and the potential for cement to become a CO2 sink under certain conditions. Techno-economic studies have estimated mineralisation storage costs at €65–€443 tCO2 avoided (excluding capture) but often neglect product value streams. Prior work also highlights the need to monitor broader environmental impacts (e.g., metal depletion, freshwater consumption) when deploying mineralisation. The paper positions its contribution as a move beyond storage-only assessments by valuing mineralisation products used as SCM in cement.

The authors model cement production integrated with CO2 mineralisation at a cement plant (1.4 Mt cement/year), capturing kiln CO2 and carbonating on-site to produce SCM that replaces a portion of ordinary Portland cement (assumed feasible up to 25% replacement based on performance constraints). Two carbonation process routes are developed: (1) Direct carbonation with slurry reaction under elevated pressure and temperature, followed by classification to ensure SCM quality; (2) Indirect carbonation extracting Mg with additives (e.g., ammonium salts), regenerating additives with heat, and subsequently carbonating via a CO2 carrier. Unusable material is stored nearby; feed minerals are transported 1200 km to reflect European availability constraints. Scenarios: Pessimistic, mid, and optimistic, varying silica content in SCMCCU (50/40/30%), SCM share in cement (10/20/25%), ETS price (0/40/89 €/tCO2), and derived cement price (63/90/138 €/t cement). ETS revenue eligibility is assumed for CaCO3 and (in optimistic/mid) by analogy for Mg carbonates; pessimistic assumes no ETS eligibility. Economic and TEA framework: The MATLAB-based model solves mass and energy balances, sizes equipment, and computes CAPEX (TCR) and OPEX to derive levelised cost of product (LCOP) and revenues. Capital cost estimation follows a hybrid FOAK-to-NOAK approach (Rubin et al.), with learning curves and an assumption that 20 plants are required to reach NOAK maturity. Total plant cost is built from total direct costs using bottom-up equipment cost curves (derived via Aspen Capital Cost Estimator regressions for unit operations such as crushers, mills, reactors, hydrocyclones, centrifuges, heat exchangers, dryers) and top-down scaling for CO2 capture and compression subsystems based on literature. CO2 capture is MEA post-combustion for the direct route and integrated aqueous ammonia for the indirect route. Operational expenditures include fixed (labour, insurance, maintenance, admin) and variable (utilities: electricity, natural gas; feedstocks; transport via truck/train/ship with distance constraints). Revenues comprise cement displacement value, ETS credits for mineralised CO2, and accounting for any storage/disposal of unusable material. LCOP annualisation uses a levelisation factor with plant lifetime and weighted cost of capital incorporating debt and equity. CO2 emissions accounting: Carbon footprinting approach adapted from Ostovari et al. considers emissions from feedstock mining and additive production, mineral and product transport, electricity and gas use, and plant construction, net of CO2 chemically bound and clinker production avoided via SCM use. Emission reductions for cement blends are computed relative to baseline OPC. Uncertainty and sensitivity: Single-factor sensitivity screening followed by Monte Carlo global uncertainty analysis (10,000 runs, UQLab) on influential parameters with probability distributions per literature. Key uncertain inputs include electricity price, interest rate, learning rate and number of plants to maturity, additive recovery, solid-liquid ratio, reaction kinetics, mineral purity, utility prices, and additive prices (e.g., ammonium sulphate). Learning curve analysis estimates how many initial plants require additional support under each scenario. Competitiveness benchmarking: The study compares CO2 mineralisation to alternative decarbonisation strategies (biofuels, calcined clay cement, MEA-CCS with offshore storage, oxy-fuel CCS with offshore storage) across ETS price ranges, including combined strategies where captured CO2 is split between geological storage and mineralisation, using consistent transport and energy assumptions.

• Profitability: Under the optimistic scenario, both routes yield positive business cases with profits of ~€129 per tonne of SCMCCU (direct) and ~€117/t (indirect), translating to ~€44 M and €39 M per year per cement plant and ~€32 and €29 per tonne of cement sold. In the mid scenario, they approximately break even (direct: €3/t SCM; indirect: €5/t). In the pessimistic scenario (no ETS eligibility), losses occur: €108/t SCM (direct) and €80/t (indirect), adding costs of ~€10 and €8 per tonne of cement.
• Optimal capacities and scalability: Economically optimal CCUM plant capacities (profit-maximising) are 136, 272, and 340 kt SCMCCU per year for pessimistic, mid, and optimistic scenarios (for both routes). In the optimistic scenario, positive business cases persist up to ~940 kt/a (direct) and ~780 kt/a (indirect). ETS revenues alone do not cover mineralisation costs; market uptake as SCM is essential.
• Emission reductions: At economically optimal capacities and current (2016) grid mixes, CO2 reductions are 15–33% (direct) and 8–23% (indirect) versus OPC. With fully decarbonised electricity and heat, reductions rise slightly to 17–36% (direct) and 12–28% (indirect). For the direct route, going beyond optimal capacity can further increase CO2 reductions (above 33%) but with diminishing economics; for the indirect route, emissions worsen beyond optimal capacity due to additive production and regeneration energy.
• ETS price thresholds: Breakeven ETS prices for the direct route range from €99/tCO2 in an otherwise pessimistic case to no ETS support needed in optimistic; the indirect route requires ~€123/tCO2 in pessimistic to none in optimistic.
• Transport distance sensitivity: In the optimistic scenario, revenues can offset mineral transport beyond 2000 km while remaining profitable. In the mid scenario, with lower revenues and higher LCOP, profitability is constrained to roughly ≤450 km with truck+train or ≤2000 km using truck+train+ship; ship transport is essential for long distances.
• Silica content trade-off: Lower silica content in SCMCCU reduces production cost (less feedstock throughput and separation), but lowers CO2 stored and ETS revenue. In the pessimistic scenario, breakeven requires silica shares below ~15% (direct) and ~21% (indirect). In the optimistic scenario, costs are offset up to silica shares of ~85% (direct) and ~68% (indirect).
• Cost drivers and uncertainties: Global sensitivity shows electricity price and interest rate as highly influential for both routes. The direct route is more capital-intensive (capture and compression), thus more sensitive to capital cost factors and learning. The indirect route is highly sensitive to ammonium sulphate price and additive recycling rate; higher solid/liquid ratios reduce costs in both. Reaction kinetics have relatively modest impact on LCOP compared to energy and finance parameters.
• Learning and first-mover economics: Assuming 20 plants to NOAK, in the mid scenario the first ~11 (direct) and ~3 (indirect) plants need additional support; in pessimistic (all 20 unviable) and optimistic (all 20 viable) cases, outcomes are uniform. This indicates ETS/CO2 prices alone may be insufficient to spur early deployments without complementary policies.
• Competitiveness: With rising ETS prices, baseline OPC costs increase by about €0.85 per t cement per €1 per tCO2 increase if no mitigation is applied. CO2 mineralisation is competitive with other options, notably calcined clay cements, achieving similar CO2 reductions at lower SCM shares (~25% vs ~50%). At high ETS prices, oxy-fuel CCS can undercut due to higher absolute abatement. Combining CO2 mineralisation with CCS (MEA or oxy-fuel) reduces overall decarbonisation cost burden; even at €200/tCO2, cement costs would increase by only ~30% relative to today’s price.

The findings demonstrate that CO2 mineralisation integrated in cement plants can deliver substantial emission reductions (8–33% at optimal scales) while generating profits under favourable conditions. The two key enablers are: (1) broad acceptance, standardisation, and market uptake of SCMCCU as a cement replacement, and (2) eligibility of mineralised CO2 for ETS credits or similar mechanisms. Economic viability is further enhanced when feed minerals are regionally available (limiting transport costs) and when SCM formulations do not require high silica shares. These results address the central question of when mineralisation forms a positive business case: revenue from cement displacement plus ETS credits can outweigh LCOP for both direct and indirect routes; in their absence (pessimistic), economics are negative. Sensitivity analyses highlight electricity price and financing costs as dominant levers, indicating the importance of energy decarbonisation, long-term power contracts, and favourable financing (e.g., lower WACC). The indirect route’s reliance on additives makes additive recovery and price crucial. Learning-curve analysis suggests early plants may require targeted support, akin to historical deployment of wind and solar. System interactions matter: mineralisation competes and complements other strategies. Combining mineralisation with CCS leverages shared capture/compression infrastructure and scale effects, reducing overall decarbonisation costs. However, simultaneous deployment with other SCMs (e.g., calcined clay) may create competition for reactive silica in cement formulations and be constrained by transport economics; technology choices may be location-specific. Mineralisation may also synergise with CO2 curing of concrete and end-of-life carbonation, potentially enhancing overall lifecycle reductions, though full LCAs are needed to confirm net benefits.

The study demonstrates that CO2 mineralisation for producing SCM can reduce cement plant CO2e emissions by 8–33% and, under supportive conditions, deliver positive profits up to ~€32 per tonne of cement. Positive business cases require: (1) standardisation and widespread acceptance of SCMCCU in cement blends and (2) eligibility of mineralised CO2 for ETS or similar crediting. Transport distance of minerals and product composition (silica share) are critical determinants of viability. Mineralisation is competitive with other abatement options and, when combined with CCS, can substantially lower decarbonisation costs for the sector. Future work should focus on: advancing TRL of product separation and overall process integration; accelerating standards and performance testing for SCMCCU blends; validating large-scale operation and learning effects; exploring location-optimised deployment with other SCMs; evaluating broader environmental impacts via full LCA; and assessing policy instruments (e.g., ETS rules for Mg carbonates, first-mover subsidies, loan guarantees) to de-risk early plants.

• ETS eligibility for magnesium carbonates is not yet established; pessimistic scenarios assume no ETS credits, significantly affecting profitability.
• The techno-economic analysis focuses on climate (CO2) impacts; other environmental impacts from mining, water use, and land use are acknowledged but not assessed in detail.
• Low TRL components (particularly product separation) rely on limited laboratory data (TRL 2–3); carbonation processes are based on bench-scale studies (TRL 4), introducing uncertainty in scale-up.
• Energy system decarbonisation scenarios are simplified (e.g., assuming zero emissions for electricity/heat in a decarbonised case); primary results use current grid emission factors.
• Equipment cost and performance are partly derived via cost curves and scaling from literature and Aspen estimates; FOAK/NOAK assumptions (20 plants to maturity) and learning rates introduce uncertainty.
• Transport and mineral availability are region-specific; assumed transport modes and distances may not generalise to all geographies.
• Financial assumptions (interest rates, DER, ROE) and energy prices strongly influence results; early deployments may face higher capital costs than assumed, requiring policy support.
• Cement blend performance limits (e.g., max ~25% SCMCCU substitution) are based on available evidence and may vary with local standards and formulations.