Geochemical carbon dioxide removal potential of Spain

Many countries have made pledges to reduce CO2 emissions over the upcoming decades to meet the Paris Agreement targets of limiting warming to no >1.5 degrees C, aiming for net zero by mid-century. To achieve national reduction targets, there is a further need for CO2 removal (CDR) approaches on a scale of millions of tonnes, necessitating a better under-standing of feasible methods. One approach that is gaining attention is geochemical CDR, encompassing (1) in-situ in-jection of CO2-rich gases into Ca and Mg-rich rocks for geological storage by mineral carbonation, (2) ex-situ ocean alkalinity enhancement, enhanced weathering and mineral carbonation of alkaline-rich materials, and (3) electro-chemical separation processes. In this context, Spain may host a notionally high geochemical CDR capacity thanks to its varied geological setting, including extensive mafic-ultramafic and carbonate rocks. However, pilot schemes and large-scale strategies for CDR implementation are presently absent in-country, partly due to gaps in current knowl-edge and lack of attention paid by regulatory bodies. Here, we identify possible materials, localities and avenues for future geochemical CDR research and implementation strategies within Spain. This study highlights the kilotonne to million tonne scale CDR options for Spain over the rest of the century, with attention paid to chemically and mineral-ogically appropriate materials, suitable implementation sites and potential strategies that could be followed. Mafic, ul-tramafic and carbonate rocks, mine tailings, fly ashes, slag by-products, desalination brines and ceramic wastes hosted and produced in Spain are of key interest, with industrial, agricultural and coastal areas providing opportunities to launch pilot schemes. Though there are obstacles to reaching the maximum CDR potential, this study helps to identify focused targets that will facilitate overcoming such barriers. The CDR potential of Spain warrants dedicated investiga-tions to achieve the highest possible CDR to make valuable contributions to national reduction targets.

Automated summary

Many countries have committed to reducing CO2 emissions in order to achieve the goals of the Paris Agreement, and Spain, with its diverse geological setting, has the potential for high geochemical carbon dioxide removal (CDR). However, there is currently a lack of pilot schemes and large-scale strategies for CDR implementation in Spain, due to gaps in knowledge and lack of attention from regulatory bodies. This study identifies possible materials, locations, and strategies for future geochemical CDR research and implementation in Spain, highlighting the potential for kilotonne to million tonne scale CDR options.