A Comparative LCA of Thermal and Mechanical Activation in Clay Material Processing

This study compares the environmental impacts of two clay activation technologies – flash calciner (thermal) and agitated bead mill (mechanical) – using clays from Brazil and Denmark as Supplementary Cementitious Materials (SCMs) for cement production. A cradle-to-gate life cycle assessment (LCA) based on openLCA software, Ecoinvent database, and industrial data was utilized to evaluate the environmental impacts to produce one kilogram of activated clay. Global warming potential (GWP, kg CO2-eq) was the primary impact category for the LCA study since it is a key driver of climate change. Moreover, a sensitivity analysis was carried out to evaluate the impact of the energy mix on the LCA outcome. For the assessed clays, the LCA shows that thermal activation yields in average 34% greater CO2 emissions than that from mechanical activation; despite the latter having an average of 26% higher total energy consumption against thermal activation. Since both technologies require similar energy for drying the clay’s moisture, the energy difference from the processes stems primarily from the agitated bead mill’s higher power demand. The sensitivity analysis shows that when electricity is sourced mainly from fossil fuels, CO2 emissions from mechanical activation can exceed those of thermal activation. Additionally, an analysis of energy consumption and operating costs reveals that, under current energy pricing, flash calcination is more cost-effective than mechanical activation. Overall, this study underscores the importance of factors such as clay composition, moisture content, and regional energy mix in assessing the environmental and economic performance of activated clays. While both activation methods present trade-offs, the high electricity demand of current mechanical activation process highlights the need for the development of more energy-efficient activation technologies that help produce more sustainable SCMs for composite cement production.