Laboratory Synthesis of Limestone for CO2 Capture and Removal: A Review of Ca-Based Mineral Carbonation

Mineral carbonation offers a thermodynamically stable, permanent route for immobilizing CO2 as solid carbonate minerals. Whether it constitutes genuine carbon dioxide removal (CDR) depends on the carbon source: net atmospheric removal requires CO2 captured from air (e.g., by direct air capture) or biogenic sources and then durably stored, whereas mineralization of fossil-derived industrial CO2 is better classed as carbon capture and storage or utilization (CCS/CCU). Calcium-bearing silicates and Ca-rich industrial residues are attractive feedstocks because their reaction with CO2 yields calcium carbonate (CaCO3), the mineral of natural limestone. In nature, Ca-silicate weathering and CaCO3 precipitation buffer Earth’s climate over millennia; engineered Ca-based carbonation seeks to reproduce this limestone-forming cycle in reactors orders of magnitude faster, enabling permanent storage on practical timescales. This review consolidates recent advances in ex situ Ca-based mineral carbonation under a unified framework in which the synthesis of “engineered limestone” is the central objective. It outlines the geochemical basis and its engineering translation, compares Ca-silicates and Ca-rich residues as feedstocks, and surveys direct and indirect routes, emphasizing conversion, energy demand, and control of CaCO3 polymorph and morphology. Techno-economic and environmental assessments, demonstrations, and challenges to gigatonne-scale deployment are summarized, offering a reference for next-generation Ca-based CDR research.