Silicate-derived calcium as a pathway to low-carbon Portland cement

Abstract Cement production accounts for 4.4% of global greenhouse gas emissions by releasing carbon dioxide from limestone and using an energy-intensive process. Decarbonization technologies, including lower-carbon alternative cements and carbon capture, have existed for decades but have not been adopted. Here we examine the viability of making ordinary Portland cement using carbon-free silicate rocks (like common basalt) instead of limestone. Our thermodynamic analysis shows that producing Portland cement from basalt could require less energy than traditional limestone production, highlighting the potential to simultaneously reduce cost and emissions. We identify a set of proven unit processes to produce Portland cement and supplementary cementitious materials from basalt minerals that could reduce the total energy demand by 30% with respect to conventional production, while eliminating process emissions entirely. Also, the ratios of calcium, iron, and aluminum in basalt are favorable for meeting the global demand for Portland cement, steel, and aluminum from one feedstock.