Carbon-negative cement manufacturing from seawater-derived magnesium feedstocks
Palash Badjatya, Abdullah Huzeyfe Akca, Daniela V. Fraga Alvarez, Baoqi Chang, Siwei Ma, Xueqi Pang, Emily Wang, Quinten van Hinsberg, Daniel V. Esposito, Shiho Kawashima
Abstract
This study describes and demonstrates key steps in a carbon-negative process for manufacturing cement from widely abundant seawater-derived magnesium (Mg) feedstocks. In contrast to conventional Portland cement, which starts with carbon-containing limestone as the source material, the proposed process uses membrane-free electrolyzers to facilitate the conversion of carbon-free magnesium ions (Mg 2+ ) in seawater into magnesium hydroxide [Mg(OH) 2 ] precursors for the production of Mg-based cement. After a low-temperature carbonation curing step converts Mg(OH) 2 into magnesium carbonates through reaction with carbon dioxide (CO 2 ), the resulting Mg-based binders can exhibit compressive strength comparable to that achieved by Portland cement after curing for only 2 days. Although the proposed “cement-from-seawater” process requires similar energy use per ton of cement as existing processes and is not currently suitable for use in conventional reinforced concrete, its potential to achieve a carbon-negative footprint makes it highly attractive to help decarbonize one of the most carbon-intensive industries.