Cement Energy & Environment

10 ~40–50% CO 2 savings[5]. Belite-rich Portland cements (RBPC) reduce firing temperature and limestone content to cut ~10% of process CO 2 [21]. Calcium sulfoaluminate/belite-ferrite (CSA or BYF) cements can substitute 20–30% of limestone and thereby cut 20–30% of emissions[22]. Emerging “carbonatable” calcium-silicate cements (CCSC) can even reabsorb CO 2 during curing, achieving ~30–50% net reduction[6]. Magnesium- based cements (from magnesite or magnesia silicates) are being engineered for carbon- negative operation: if produced from Mg-silicates (MOMS), the process could theoretically lock more CO 2 than is emitted[23]. Alkali-activated “geopolymer” concretes (using fly ash or slag) can also lower emissions by ~40–80%, though they depend on byproduct supply (not shown). Notably, the concrete infrastructure itself can sequester CO 2 over its lifetime via natural re- carbonation, and some companies are developing accelerated carbonation processes (e.g. CO 2 - injected curing) to lock in cement CO 2 [24]. Aside from supply solutions, demand-side strategies can alleviate emissions. Optimized building design and construction can use less cement (materials efficiency, long service life)[25]. Substituting concrete with steel or engineered timber where suitable, and maximizing reuse of concrete components, can reduce cement demand. For example, constructing buildings for longer lifetimes and reusing concrete elements (rather than demolition) would slash aggregate waste and fresh cement needs[25]. Increased circularity — grinding and reusing demolition concrete as aggregate or even as cementitious filler — can also save primary resources[25]. Studies emphasize a “whole-of-system” approach: demand reduction and material recovery must go hand in hand with greening production to meet climate targets[25][20]. MATERIALS AND METHODS This review isbasedonanextensivesurveyof recent literature (2020–2025) on sustainable cement and concrete. Academic journals, industry reports, and technical roadmaps were examined using keyword searches (e.g. “cement decarbonization,” “supplementary cementitious materials,” “green concrete”) in databases like Google Scholar and Scopus. Relevant sources were selected for their technical rigor, recency, and focus on low-carbon cement technologies and policies. Emission factors, material performance data, and case studies were extracted and synthesized. Given this is a qualitative review, no new experimental data were generated; the emphasis is on summarizing and comparing reported results. RESULTS AND DISCUSSION Fuel consumption by US. Cement plants in 2000 and 2022 Category Fuel Energy Consumption (TBtu) Share of Total Energy Consumption(%) Scope 1: Con- ventional fuels Coal Petcoke Oil Natural gas 214.7 49.0 4.57 12.3 100.6 50.8 1.25 77.5 57.4% 13.1% 1.2% 3.3% 31.5% 15.9% 0.4% 24.2% Scope 1: Waste fuels Tires Solid waste Liquid waste 11.2 11.6 29.5 12.3 12.8 24.5 3.0% 3.1% 7.9% 3.8% 4.0% 7.7% Scope 2 Purchased electricity 41.0 39.9 11.0% 12.5% Total All 373.9 319.8 100% 100% Source: USGS. (2024). “Cement 2022 tables-only release.” Minerals Yearbook 2022, v. I, Metals and Minerals. Available at: https:// www.usgs.gov/centers/national-minerals-information-center/cement-statistics-and-information ; USGS. “Cement Minerals Yearbook 2000.” Available at https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/mineral-pubs/ce- ment/170400.pdf.