Liu et al. (2026): A new pathway to enhance the oceanic carbon sink: inorganic carbonate precipitation driven by calcium–alkali coupling

Shan Shan Liu, Jin Ming Song, Xue Gang Li, Hua Mao Yuan, Li Qin Duan et al., IN: Journal of Environmental Management, https://doi.org/10.1016/j.jenvman.2026.130294

Anthropogenic CO₂ emissions are intensifying climate change, creating an urgent need for scalable and efficient strategies to enhance the oceanic carbon sink. This study proposes and evaluates a new calcium–alkali coupling pathway in which the co-addition of Ca²⁺ and OH⁻ promotes the conversion of seawater dissolved inorganic carbon (DIC) into solid CaCO₃. This process perturbs carbonate-system equilibrium and subsequently drives additional atmospheric CO₂ uptake during system re-equilibration. Unlike conventional alkalinity-enhancement approaches that mainly retain absorbed CO₂ as dissolved bicarbonate and carbonate species, the pathway examined here emphasizes carbonate precipitation as a major mode of DIC removal. Laboratory experiments, mesocosm simulations, and a 1000 m³ offshore field demonstration in the southern Yellow Sea were conducted to assess carbon-removal efficiency and short-term environmental responses. Under a dosing scheme of 1.79 mmol Ca²⁺ and 3.58 mmol OH⁻ per litre of seawater, DIC in the 1000 m³ field system decreased by 1763 μmol kg⁻¹ and was converted into CaCO₃, corresponding to an estimated uptake of 77.6 kg atmospheric CO₂.

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