Energy demand and savings opportunities in the supply of limestone and olivine-rich rocks for geochemical carbon dioxide removal

The large-scale implementation of geochemical Carbon Dioxide Removal (CDR) approaches such as Enhanced Weathering (EW) and Ocean Liming (OL) will require the extraction and processing of large amounts of limestone and olivine-rich rocks. Based on a literature review, surface mining, comminution, their related sub-stages, and long-haul transportation have carefully been surveyed to elucidate the order of magnitude of the energy demand, the technical challenges posed by each operation, and the potential energy-savings achievable by applying opportune strategies. This work confirms the significant energy-saving opportunities in fine and ultrafine grinding (one of the most energy-consuming activities along the raw material supply chain) as underlined by previous studies, and, in addition, it focuses on limestone and olivine-rich rocks providing new outcomes, it analyses data from a climate change perspective and extends calculations and discussion to transportation. The results show that the implementation of energy-saving strategies (cutting-edge energy efficiency solutions and best practices) to comminute such materials for OL and EW purposes in the near-medium term (2025-2050) would reduce the average electricity demand by 33%-65% in case of low carbon removal target (up to 27 MtC yr-1) and substantial energy efficiency improvement, and by 33%-36% in case of high carbon removal target (up to 69 MtC yr-1) and poor energy efficiency improvement.