Issue Date: June 9, 2008
Iron In The Ocean
Having read "Fertilizing the Ocean with Iron" I was pleased to learn that iron fertilization in areas of the ocean experiencing iron deficiency is having a resurgence (C&EN, March 31, page 30). It is the only reasonable way offered to date to remove carbon dioxide from the atmosphere efficiently and at a reasonable cost while creating something of value.
Let's hope the experiments are successful. I see a serious problem in the experimental design, however. Is enough time being allowed for the process to reach equilibrium? And what are the equilibrium products? In the short run, micrometer-size phytoplankton are formed that, due to their size, will settle very slowly and oxidize easily.
At equilibrium, the food chain will have developed, with the arrival of aquatic animals that will form large carbon-containing debris that should sink to the sea bottom rapidly, before oxidation occurs. It might take years for the system to reach maximum debris production. If this process is successful in, say, the equatorial Pacific where adequate nitrate and phosphate nutrients are present, a huge new fishery would be created.
I also see a problem with using the proposed iron salt in this work; it will rapidly disappear—as discovered in the initial work—so the fertilization period will have a short life. A superior method would be to use the published procedure of using insoluble iron oxides or silicates from which the phytoplankton can extract the iron and that are made to float by incorporating them in a polymer foam. The composite could be designed to disintegrate or sink under the influence of sunlight and saltwater in a specific time, so the iron would not float out of the designated area and create problems elsewhere.
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