Campbell et al. (2026): Harnessing naturally occurring sodium carbonate and bicarbonate for gigatonne-scale carbon dioxide removal
James Campbell, Spyros Foteinis, Reinaldo Juan Lee Pereira, Mohamad Katish, Phil Renforth, IN: EarthArXiv, https://doi.org/10.31223/X5276Q
Ocean alkalinity enhancement is a promising carbon dioxide removal (CDR) approach, but scaling up to gigatonnes (Gt) of CO₂ per year will require safe, sustainable, and abundant alkaline feedstocks. Here, the authors propose the use of a relatively unexplored resource for OAE, namely naturally occurring sodium (bi)carbonates. They identified and mapped 109 such deposits globally, although quantitative resource information is available for only 16. Quantified deposits collectively contain >200 Gt of sodium (bi)carbonate-rich minerals and brines, dominated by trona (Na₂CO₃·NaHCO₃·2H₂O) and nahcolite (NaHCO₃) mainly concentrated in the USA, China, Turkey, and Kenya. They then assessed three OAE pathways using trona as a feedstock, i.e., 1) Mining, crushing, and ocean dispersal of trona (gross CDR capacity 0.16 tCO₂ t⁻¹); 2) Calcine trona with carbon capture and storage to produce soda ash (Na₂CO₃) (0.31 tCO₂ t⁻¹) prior to dispersal; and 3) Purification of soda ash via dissolution, crystallisation, and drying prior to dispersal. Using Green River, Wyoming, USA (~116 Gt of bedded trona) as a case study, life cycle assessment informed on the net-negativity of each pathway.