Geochemical carbon dioxide removal potential of Spain

Abstract

Many nations have pledged to reduce carbon dioxide (CO2) emissions over the remainder of the century to meet the Paris Agreement targets of limiting warming to no more than 1.5°C, aiming for net zero by mid-century. This is the long-term commitment of the European Union (EU), which is targeting climate-neutrality by 2050, in line with the commitment to global climate action under the Paris Agreement and the European Green Deal. For many European nations, this means a critical examination of all potential pathways to net zero (or net negative), including assessing methodological options, material suitability and physical footprints.To achieve national and EU reduction targets, there is a further need for CO2 removal (CDR) approaches on a scale of millions of tonnes, necessitating a better understanding of feasible methods and materials for utilization. One approach that is gaining attention is geochemical CDR, encompassing (1) in-situ injection of CO2-rich gases into Ca and Mg-rich rocks for geological storage by mineral carbonation, (2) ex-situ approaches such as ocean alkalinity enhancement and ocean liming, enhanced weathering and carbonation of alkaline-rich materials, and (3) electrochemical separation processes. In this study, we examine the geochemical CDR potential of Spain. As an EU Member State, Spain is bound to adopt the national energy and climate plans to make considerable progress on its climate actions. Here, an assessment of the reactivity potential of materials and utilization sites in Spain has been made based on the suitability of hosted materials in terms of spatial and volumetric availability, chemistry, modal mineralogies and mineral kinetics.Spain hosts a potentially high geochemical CDR capacity thanks to its varied geological settings and its high tonnage production of industrial alkaline wastes, suitable due to their high Ca and Mg contents and varying occurrence of kinetically favourable minerals (e.g., serpentine, brucite, olivine). There are notional kilotonne to million tonne scale CDR options for Spain over the rest of the century, with attention paid to mafic, ultramafic and carbonate rocks, mine tailings, fly ashes, slag by-products, desalination brines and ceramic wastes, with industrial, agricultural and coastal areas providing opportunities to launch pilot schemes. Materials and land space are distributed across the Spanish mainland and islands, with particularly high potential for Galicia, Andalucía, Murcia and the Canary Islands regions. The CDR potential of Spain warrants dedicated investigations to achieve the highest possible CDR to make valuable contributions to national reduction targets. Results can also be used to further define Spain’s overall climate targets and initiate future CDR plans and projects for academia, industry, government and other sectors of interest.This work forms part of the DETAILS project (Developing enhanced weathering methods in mine tailings for CO2 sequestration; Marie Skłodowska-Curie grant agreement ID: 101018312).