The alternative refractory magnesia sources in the context of decarbonization

Magnesium is essential for various industries, notably in the form of magnesia (MgO), an important refractory aggregate. Natural magnesia is the name given to the MgO produced from the calcination of Magnesite (MgCO3), the most relevant source. However, natural magnesia production emits significant CO2, exacerbating global warming. Consequently, alternative magnesia sources should be considered when looking for environmental gains. Luckily, magnesium is an abundant element, representing 4.66% of the continental crust, and is also present in seawater in a concentration of 1290 ppm. MgO produced from sources other than magnesite is called synthetic magnesia. It can be obtained from seawater and brines or from magnesium silicates. The first is based on the precipitation of brucite (Mg(OH)2) with an alkali agent and subsequent calcination. The second has the same basis but with a previous leaching step. Synthetic magnesia remains energy-intensive and costly, and despite avoiding the geogenic CO2 emissions from magnesite, the indirect emissions can raise the CO2 footprint higher than natural magnesia, depending on the alkali agent used and energy source. Carbonation methods have also been studied in synthetic magnesia production and preliminary results are promising. Efforts to decarbonize magnesia production may include optimizing synthetic magnesia processes. Although these methods face challenges, they offer potential for reducing CO2 emissions in the refractory industry. Within the CESAREF consortium, this study evaluates the alternative magnesia sources and their role in mitigating CO2 emissions, providing insights into sustainable practices for refractory material production.