## 1 Introduction  
According to the International Energy Agency [1], achieving the Paris Climate Agreement targets of global warming below 2 \({}^{\circ}\)C by 2100 while developing efforts to limit temperature rising to 1.5 \({}^{\circ}\)C [2] implies wide scale deployment of CO2 capture, utilization, and storage (CCUS). The scenarios developed by the IEA by the 2060 CCUS should contribute to 14% of the required reduction in CO2 emissions to achieve a scenario where temperatures are less than 2 \({}^{\circ}\)C, or 32% to achieve the 1.5 \({}^{\circ}\)C limit scenario. Portugal has been on the forefront of policies to reduce CO2 emissions, having established a roadmap to reach carbon neutrality by 2050 [3]. This policy has been reinforced by the Green Deal announced in December 2019 by the European Commission, which sets the same carbon neutrality target by 2050 for the European Union [4]. The roadmap does not explicitly consider CCUS as one of the technologies that should contribute to carbon neutrality in Portugal, although earlier studies have demonstrated that CCUS will be required in some industry sectors (e.g., cement) as early as 2030 [5; 6]. According to the European Union carbon market database (EU ETS), in 2018, the Portuguese CO\({}_{2}\) emissions from the industrial and power sectors amounted to 26.2 Mt CO\({}_{2}\)[7], with the most important emissions cluster located in southern Portugal, extending from Setubal to the Sines industrial area, being responsible for 44% of all emissions in the country (Figure 1a). Although the main point source in the region, the Sines Coal Power Plant, is to be decommissioned in 2023, the remaining sources will account for more than 30% of all emissions from industrial sources (Figure 1b). Furthermore, the socioeconomic relevance of the industry to the region imposes the need to seek alternatives to decarbonization in the region. The possibility of capturing CO\({}_{2}\) at the Sines and Setubal sources and storing it in offshore deep saline aquifers was addressed previously [8; 9], but was decided against due to low storage capacity and high storage costs. The possibility of CO\({}_{2}\) transport to other parts of the country with more favorable geological storage conditions was studied in Seixas et al. [6] and is being further pursued in the STRATEGY CCUS project [10], funded by the European Union's Horizon 2020 to study the development of CCUS in Southern and Eastern Europe, including a promising region in Portugal. Nonetheless, the multiple ultramafic and mafic rock massits in Alentejo could provide an alternative for CO\({}_{2}\) storage by mineral carbonation. The potential of ultramafic and mafic rocks for CO\({}_{2}\) storage rests in their ability to stabilize CO\({}_{2}\) via mineral carbonation (e.g., [11; 12; 13; 14]). These rocks are enriched in Ca\({}^{2+}\), Mg\({}^{2+}\), and Fe\({}^{2+}\) silicate minerals, which react with CO\({}_{2}\) precipitate carbonate minerals [15], leading to the trapping of the CO\({}_{2}\) in a solid phase at a much faster rate than can be expected in sedimentary silicate rocks. The feasibility of this process was demonstrated in the CarbFix (Iceland) project [16] and Wallula (USA) project [17], in a process designated as in situ mineral carbonation, in which CO\({}_{2}\) is dissolved in water and injected into basalts. However, extensive studies have also addressed an ex situ process, in which the ultramafic and mafic rocks are mined and the mineral carbonation process takes place in plants under optimized pressure and temperature conditions [18; 19; 20]. A third possibility that has been put forward as a geo-engineering technique is the utilization of ultramafic rocks to sequester CO\({}_{2}\) through enhanced weathering, in which the mined and crushed rock is spread in large areas under atmospheric conditions to react with CO\({}_{2}\), promoting direct CO\({}_{2}\) capture from the air [21; 22].