We need to become a carbon-neutral society as soon as possible to minimize the effects of climate change. This necessity implies urgent action to a complex problem that requires multiple solutions. Among the available solutions, Carbon Capture and Storage (CCS) is considered as a key technology to reach zero emissions because not only will it contribute to reduce CO2 emissions of the energy sector, but also will permit eliminating emissions in the hard-to-abate industry. The hard-to-abate industry represent some 10% of the total CO2 emissions, i.e. 4 Gt/yr. Therefore, we have to rely on CCS at the gigatonne scale to reach net-zero emissions. Thus, we need as much CO2 storage capacity as possible while reducing the main risks of CCS, i.e. CO2 leakage and induced seismicity. In conventional CO2 storage in deep sedimentary formations, CO2 is lighter than water and, thus, the risk of CO2 leakage is an issue. Alternative storage concepts have been proposed to reduce the CO2 leakage risk: (i) achieving a fast fixation of carbon through mineralization and (ii) injecting CO2 already dissolved into the brine. In both cases, the injection rates should be low because CO2 dissolution into brine is around 4%, so the amount of injected CO2 is 25 times smaller than that of CO2 if injected in free phase. To circumvent this issue, CO2SINk proposes a novel CO2 storage concept in deep volcanic areas where water stays in supercritical state, i.e. pressure>22.1 MPa and temperature>374 ºC, because at these conditions CO2 becomes denser than water and, therefore, sinks. This concept not only reduces the leakage risk, but also permits injecting large amounts of CO2, which is necessary to effectively reduce CO2 emissions to mitigate climate change. This novel storage concept would benefit society by (1) enhancing the CO2 storage options and (2) reducing the risk of CO2 leakage. CO2SINk is in line with the European Green Deal – the EU´s roadmap in transforming to a sustainable economy and industry –, which sets clean and secure energy supply and CCS among the priorities. These priorities are also dealt with the 7th and 13th UN Sustainable Development Goals targeting “affordable and clean energy” and “climate action”, respectively. The overall objective of this Proof of Concept is to explore the commercialization possibilities of this novel concept of geological CO2 storage.
