Ocean alkalinity enhancement: Insights and considerations for application

Reaching net-zero emissions by 2050 requires both steep reductions in anthropogenic CO₂ and active carbon dioxide removal (CDR) to offset hard-to-abate sources, with CDR projected to account for roughly 15–20% of current greenhouse gas emissions. Ocean alkalinity enhancement (OAE), which accelerates mineral weathering to increase oceanic CO₂ uptake, is among the most promising marine CDR strategies, yet large-scale deployment remains largely conceptual and a consolidated implementation framework is lacking. Here, we develop a comprehensive OAE process chain structured around five themes - initial planning and considerations, preceding steps, deployment, monitoring, reporting and verification (MRV), and carbon uptake - systematically identifying the environmental, technical, and social considerations for mineral-based OAE across coastal, river, and open-ocean settings. Our synthesis shows that mineral dissolution, environmental interactions, and CO₂ uptake potential have received much attention through experiment and model studies. In contrast, critical gaps remain in techno-economic analyses covering mineral acquisition, transport and deployment logistics, and resource capacities, as well as in social and legal dimensions, including societal acceptance, regulatory frameworks, and MRV accountability. We conclude that OAE deployment as currently envisioned is likely unfeasible, founded on unrealistic assumptions regarding scale and logistics, though the fundamental CDR potential of OAE remains compelling. Large-scale application will require approaches that integrate into existing infrastructure as well as product-, service- and revenue-streams, diverging substantially from current paradigms. We identify the absence of field-scale experiments as the most critical bottleneck limiting the development and maturation of OAE.