Alkalinity factory can achieve positive climate benefits within decades

Abstract

Ocean alkalinity enhancement is a thriving pathway for mitigating climate change. The alkalinity factory promises controllable environmental impacts and cost-effective monitoring, reporting, and verification. However, research gaps remain in the identification of the climate benefits of the alkalinity factory, and filling these gaps is essential for allocating human efforts toward mitigation. In this study, we employed a life cycle assessment approach to evaluate the climate contributions of several pre-configured alkalinity factories, and milled olivine was taken as a stable alkalinity source, named the marine alkalinity reinforcement system (MARS). The results indicate that the MARS can capture an average of 153.5 tons of CO₂ over its lifespan, and a medium-sized (50 m³) MARS filled with 25 μm olivine can minimize carbon and total environmental footprints. In addition, the payback periods for these footprints range from 1.1 to 6.2 years and from 4.1 to 22.5 years, respectively, depending on the olivine-to-seawater ratio. The use of ultra-fine olivine (5 μm) and a high olivine-to-seawater ratio (4:1) significantly increased the carbon sequestration rate but also resulted in a high olivine comminution energy consumption and engineering challenges. Our findings reveal that the alkalinity factory is a viable solution in marine carbon dioxide removal when configurations can ensure positive environmental benefits.