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Fertilising The Oceans with Iron to Capture Carbon by Promoting Phytoplankton Growth

by Rami Elias Kremesti M.Sc., CSci, CEnv, CWEM

Introduction

Many parts of the ocean experience iron deficiency, particularly in open ocean areas. While iron is abundant on Earth, it’s less available in the ocean due to reactions with oxygen and formation of poorly soluble minerals. This can limit the growth of phytoplankton, which are the corner stone for the marine food web and carbon cycling.

I was recently watching Sir David Attenborough’s 2025 movie Ocean where he said something that caught my attention: the oceans’ whales fertilize the water with their feces which contains iron, a necessary nutrient for phytoplankton, which themselves are the building block of life in the ocean. The idea hit me: what if we fertilise the ocean with Iron? More phytoplankton means more captured atmospheric CO2…

Biochemistry

Iron plays a crucial role in phytoplankton’s growth and photosynthesis, acting as a necessary co-factor for various enzymes. It’s involved in energy production, biochemical catalysis, and the synthesis of chlorophyll. Iron deficiency can limit phytoplankton growth and ocean productivity, impacting the marine food web and carbon sequestration.

Ideas

We can add iron to the oceans through several ways: add Ferric salts, install iron rigs that can corrode slowly and release iron into the ocean, or we can accelerate this process through electrolysis: install floating solar powered rigs that generate DC current which can dissolve attached iron electrodes.

The Maths

Iron fertilization, the practice of adding iron to nutrient-poor regions of the ocean to stimulate phytoplankton growth, is a proposed method for capturing CO2. Estimates suggest that iron fertilization could potentially remove 0.1 to 5+ billion metric tons of CO2 per year, with 1 gigatonne (1 billion tons) per year considered most likely. This translates to a potential reduction of 10 to 50 percent of current anthropogenic CO2 emissions.

Carbon Sequestration:

When phytoplankton die, they sink to the ocean depths, carrying the carbon they have absorbed with them. This process, known as the biological pump, can help remove CO2 from the atmosphere and store it in the deep ocean for extended periods. Alternatively, phytoplankton get metabolized by various sea creatures that capture the metabolized CO2 in their own bodies. A dead wale that sinks to the bottom of the oceans buries tons of CO2…

Environmental Concerns:

While iron fertilization holds promise for carbon capture, there are also environmental concerns, such as potential impacts on other marine ecosystems and the possibility of nutrient robbing, where iron fertilization might divert nutrients from other life support systems that need them.

Conclusion

Solving climate change has become a survival necessity for the 21st century. As world atmospheric temperatures rise due to Green House Gas emissions, robust solutions for capturing CO2 become more and more necessary and vital for survival of many species including us humans. Climate change leads to severe environmental impacts caused by severe weather like storms and droughts.

About the Author

Rami Elias Kremesti is a chemist by profession and holds a deep reverence for nature. He works as a water treatment consultant based out of High Wycombe in the UK.

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