River alkalinity enhancement as a carbon dioxide removal strategy: a Norwegian case study

Summary

Effective carbon dioxide removal (CDR) strategies are urgently needed to reduce the risks of climate change. Here, we propose a new strategy for ocean alkalinity enhancement that targets the land-to-ocean component of the inorganic carbon cycle: river alkalinity enhancement (RAE). RAE adapts freshwater acidification mitigation technology to capture CO2 through mineral weathering and by increasing rivers' capacity to retain and transport alkalinity to long-term storage in the ocean. Global-scale modelling of RAE potential indicates that millions of tonnes of CDR per year is possible. We present data from a 2025 trial in Norway showing that RAE delivers ecological co-benefits, while meeting CDR criteria, including safety, scalability, permanence, and a straightforward quantification approach based directly on water chemistry measurements. We discuss lessons learned and methods for improving the CDR efficiency of future projects in Canada and elsewhere.