So, take an area of ocean 2500 – 5000 km², depleted of phytoplankton, and fertilize with a mix of 100 parts volcanic ash to 1 part iron sulphate, and monitor it over a decade. if the ratio of 300,000:1 above is correct, then you’ll need 333 kt of fertilizer to yield your 1 Gt CO2 sequestration.
