Cement Energy & Environment

11 Table 1. Summary of cement decarbonization approaches and their CO 2 reduction potential. Data compiled from recent literature. Source: Compiled from the cited literature above (e.g. CATF 2024; Volaity et al. 2025; Marandi & Shirzad 2025). Approach Description CO 2 Reduction Potential Sources Energy efficiency upgrades Better kilns, preheaters, waste- heat recovery ~5–10% [3] (up to 8%) Alternative fuels (biomass, waste) Replace coal/petcoke with bio- mass, refuse fuels ~10–20% CATF analysis (2024)[3] Clinker substitution (SCMs) Blend in slag, fly ash, calcined clays, limestone Up to ~50% (e.g. LC³) [5][4] Alternative clinkers (e.g. BYF, CCSC, MOMS) Low-CO 2 cement chemistries (CSA, carbonatable silicates, Mg-oxides) 20–100% (some net negative) [21][6][23] Electrification (electric kilns, H 2 ) Use renewable electricity or hydrogen for heat ~100% (if fully green) [7] Carbon capture and storage (CCS) Capture kiln CO 2 for storage or utilization Up to ~90% (point-source capture) [7] Table 1 summarizes key decarbonization approaches and their emission-reduction potential. Incremental strategies like energy efficiency and fuel switching offer limited gains: retrofits of kilns and heat recovery might cut emissions by on the order of only 5–10%[3]. Alternative fuels (e.g. biomass, refuse-derived fuel) can offset some fossil fuel, perhaps another ~10–20%, but their supply and net benefit are limited. In contrast, clinker substitution with SCMs can achieve larger cuts: a 50% replacement of Portland cement with limestone and calcined clay (LC³) reduces cement’s carbon footprint by ~40–50%[5]. Extensive use of fly ash or slag at concrete mixing can also trim 20–30%. Fully replacing clinker with novel cement chemistries yields still bigger drops: as noted, innovative cements such as CCSC or magnesium-based systems can eliminate a majority of process CO 2 and even be carbon-negative[6][23]. Electrification of heat (using electric induction or resistive kilns, or hydrogen fuel) in principle could eliminate fuel CO 2 entirely; pilot projects are exploring this route, but full-scale adoption awaits low-carbon power and new reactor designs[7]. Figure 2. IEA/CSI decarbonisation scenarios for cement. Current measures (ref tech scenario) only modestly reduce CO 2 (red area) while innovative pathways (green) are needed to meet a <2°C trajectory[26]. Figure 2 (IEA/CSI roadmap) illustrates that conventional levers (efficiency and fuel switching, red band) provide only small reductions. Deep cuts (green area) depend on breakthrough technologies — e.g. electrified processes, radically low-clinker cements, and CCS[26]. This emphasizes that reaching net- zero by mid-century will require deploying these advanced methods at scale. Carbon capture and storage (CCS) at the plant is one such strategy: when applied to kiln flue gas, CCS can capture up to ~90% of emitted CO 2 . Demonstration projects in Europe and elsewhere show the concept’s promise, though high costs and lack of storage infrastructure remain challenges[7]. RTS 800 2015 2020 2025 2030 Year 2035 2040 2045 2050 1200 1600 2000 2400 Energy efficiency Direct CO 2 emissions (Mt CO /yr) Fuel Switching Clinker to cement ratio reduction Innovative technologies 2DS B2DS - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _ - _