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Carbon dioxide (CO2) capture and sequestration includes a portfolio of technologies that can potentially sequester billions of tonnes of CO2 per year. Mineral carbonation (MC) is emerging as a potential CCS technology solution to sequester CO2 from smaller/medium emitters, where geological sequestration is not a viable option. In MC processes, CO2 is chemically reacted with calcium- and/or magnesium-containing materials to form stable carbonates. This work investigates the current advancement in the proposed MC technologies and the role they can play in decreasing the overall cost of this CO2 sequestration route. In situ mineral carbonation is a very promising option in terms of resources available and enhanced security, but the technology is still in its infancy and transport and storage costs are still higher than geological storage in sedimentary basins ($17 instead of $8 per tCO2). Ex situ mineral carbonation has been demonstrated on pilot and demonstration scales. However, its application is currently limited by its high costs, which range from $50 to $300 per tCO2 sequestered. Energy use, the reaction rate and material handling are the key factors hindering the success of this technology. The value of the products seems central to render MC economically viable in the same way as conventional CCS seems profitable only when combined with EOR. Large scale projects such as the Skyonic process can help in reducing the knowledge gaps on MC fundamentals and provide accurate costing and data on processes integration and comparison. The literature to date indicates that in the coming decades MC can play an important role in decarbonising the power and industrial sector.

Italian sinkholes, which are mainly related to karst phenomena (i.e., solution sinkholes, collapse sinkholes, etc.), are widespread along the Apennine ridge and in pedemontane areas where there are carbonatic bedrock outcrops. However, other collapses, which seem unrelated to karst dissolution, have been identified in plain areas with a thick sedimentary cover over buried bedrock. The main goal of this work is to study the geological, geomorphological, and structural setting of these areas to identify the possible mechanism of the generation and evolution of these collapses. About 750 cases were identified by research based on historical archives, specific geological literature, and information from local administrations. Geological, geomorphological, and hydro-geochemical surveys were conducted in 300 cases, supported by literature, borehole, and seismic data. A few examples were discarded because they could be ascribed to karst dissolution, volcanic origin (i.e., maar), or anthropogenic causes. Field studies regarding the other 450 cases are in progress. These cases occur along the Tyrrhenian margin (Latium, Abruzzo, Campania, Tuscany) in tectonic, coastal, and alluvial plains close to carbonate ridges. These plains are characterized by the presence of pressurized aquifers in the buried bedrock, overlaid by unconsolidated sediments (i.e., clay, sands, pyroclastic deposits, etc.). The majority of these collapses are aligned along regional master and seismogenetic faults. About 50% of the studied cases host small lakes or ponds, often characterized by highly mineralized springs enriched with CO 2 and H 2 S. The Periadriatic margin does not seem to be affected by these phenomena, and only a few cases have been found in Sicily, Sardinia, and Liguria. The obtained scenarios suggests that this type of collapse could be related to upward erosion through vertical conduits (i.e., deep faults) caused by deep piping processes whose erosive strength is increased by the presence of acidic fluids. In order to distinguish these collapses from typical karst dissolution phenomena, they are defined as deep piping sinkholes (DPS).

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The Italian Geological Survey (APAT) carried out field surveys and analysis of collapse phenomena (sinkholes) in Italy. The main goal of the project is to collect geological, geomorphological, geochemical and hydrogeological data about the sinkhole-prone areas in Italy in order to develop a spatial database of the characteristics of each phenomenon. The preliminary results of this study provide information on the distribution, geological setting, and monitoring and remediation actions associated with these natural collapses in Italy. Many Italian regions are affected by these natural disasters. Some of them are caused by karst collapses or anthropic activity. However, some occur in areas characterized by buried carbonate bedrock (up to 190 m), as well as by peculiar geological–structural and geochemical scenarios. In these areas it is not reasonable to ascribe the formation mechanism to karst activity. Instead, these types of cavities quickly develop in terrains with a variable granulometry, often in connection with upwelling fluids. In this work some natural specific cases have been studied in order to define the relationships between the geology (regional tectonic elements, mineral spring waters and strong gas vents) and the genesis of the sinkholes. A first attempt of sinkhole classification is also presented.