Carbon Sequestration in Penghu Basalt: Integrating CO2 Mineralization with Sustainable Brine Management

To address long-term geological carbon storage under net-zero emission scenarios , this study proposes an innovative accelerated CO2 mineralization and storage technology that uses Penghu basalt as the storage medium, combined with supercritical carbon dioxide and waste desalination brine. Through a laboratory-scale high-pressure automatic injection system, a CO2-brine mixed fluid is injected into basalt cores under simulated temperature and pressure conditions corresponding to a depth of 1,500 meters, promoting reactions between carbonate species and metal ions such as Ca, Mg, and Fe to form stable carbonate minerals, thereby achieving long-term and secure carbon fixation.To evaluate the storage capacity, this study adopts a volumetric mass-balance approach. Based on the representative chemical composition of Penghu basalt, the best-performing stratigraphic unit indicates a mineralized CO2 storage potential of approximately 7,800 MtCO2. Under Taiwan’s current carbon fee (approximately USD 9-10 per tCO2e, equivalent to about NTD 300), this corresponds to a potential avoided carbon cost on the order of USD 70-80 billion.This technology simultaneously converts waste brine into a reaction medium, reducing impacts from marine discharge and avoiding competition for freshwater, thus integrating carbon storage with water resource sustainability. The research outcomes are expected to provide a concrete technical basis for the development of mineralization-based CCUS and carbon credit mechanisms in Taiwan’s offshore islands and coastal regions.