Ocean fertilisation: Promoting the growth of photosynthetic organisms (i.e. macroalgae) for increased carbon uptake by enhancing ocean conditions for uptake with iron, nitratesor phosphates.
In other words, enhancement of nutrient supply to the near-surface ocean with the aim of sequestering additional CO2 from the atmosphere stimulated through biological production. Methods include direct addition of micro-nutrients or macro-nutrients. To count as CDR, the biomass must reach the deep ocean where the carbon has the potential to be sequestered durably.
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