Limestone can be used to capture carbon dioxide (CO2) directly from the air through a process called lime looping. In this study, Dr. Akhtar investigated two factors that can reduce the efficiency of this technology: the size of the limestone particles and naturally occurring impurities in the rock. We found that finely ground limestone captured substantially more CO2 because larger particles developed carbonate coatings that prevented them from fully reacting. We also found that silica and other impurities can react with lime during heating, further reducing the amount of material available to capture CO2.
These results show that particle size and limestone purity are important considerations when selecting materials for large-scale lime looping, and provide guidance for making this carbon removal technology more efficient.