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Geo-Engineering Against Climate Change: Seeding The Oceans With Iron May Not Address Carbon Emissions

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SYDNEY, Australia -- Numerous geo-engineering schemes have been suggested as possible ways to reduce levels of the greenhouse gas carbon dioxide in the atmosphere and so reduce the risk of global warming and climate change. One such technology involves dispersing large quantities of iron salts in the oceans to fertilize otherwise barren parts of the sea and trigger the growth of algal blooms and other photosynthesizing marine life. Photosynthesis requires carbon dioxide as its feedstock and when the algae die they will sink to the bottom of the sea taking the locked in carbon with them.

Unfortunately, present plans for seeding the oceans with iron fail to take into account several factors that could scupper those plans, according to Daniel Harrison of the University of Sydney Institute of Marine Science, NSW. Writing in the International Journal of Global Warming, Harrison has calculated the impact of iron seeding schemes in terms of the efficiency of spreading the iron, the impact it will most likely have on algal growth the tonnage of carbon dioxide per square kilometer of ocean surface that will be actually absorbed compared to the hypothetical figures suggested by advocates of the approach.

"If society wishes to limit the contribution of anthropogenic carbon dioxide to global warming then the need to find economical methods of carbon dioxide sequestration is now urgent," Harrison's new calculations take into account not only the carbon dioxide that will be certainly be sequestered permanently to the deep ocean but also subtracts the many losses due to ventilation, nutrient stealing, greenhouse gas production and the carbon dioxide emitted by the burning of fossil fuels to produce the iron salts and to power their transportation and distribution at sea.

His calculations suggest that on average, a single ocean iron fertilization will result in a net sequestration of just 10 tonnes of carbon per square kilometer sequestered for a century or more at a cost of almost US$500 per tonne of carbon dioxide. "Previous estimates of cost fail to recognize the economic challenge of distributing low concentrations of iron over large areas of the ocean surface and the subsequent loss processes that result in only a small net storage of carbon per square kilometer fertilized," says Harrison.

Others have addressed the maximum possible contribution by modeling and the generally accepted figure is around 1 billion tonnes of carbon, but those calculations do not take into account the losses discussed by Harrison. The real limit would be when the macro-nutrients are exhausted, what then is the flux of macro-nutrients into the iron limited regions per year? "Under ideal conditions the cost could be lowered and the efficiency increased but the availability of ideal conditions will be small," says Harrison.

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Reader Comments

5 people have commented so far. cloud add your comment

Read about this idea several years back. Sounded like a possibility worth looking into. I think some monies should be sourced into the project myself for limited regional tests but boy good luck with the amount of political biologists with that one. I would love a job doing field test studies on algae blooms and microscopic organisms as it pertains to current and future amounts of CO2. Also a support position for the team in the field.
   comment# 2   - john mason · folsom, usa · Dec 20, 2012 @ 3:46am

It would not take much to use the current ships, that are moving goods to add just enough iron over a large area in small amounts to boost the up take of carbon. Oil tankers make round trips use them to seed the iron. It would be more effective adding a little at a time over very large areas. Cargo and oil ships often carry more goods one way than the other so a few hundred tons of iron should be little added cost to haul and spread. It would be spread or broadcast as the ship travels where it would anyway. So it may yet really work if in fact it is needed as a tool to take up some carbon.
   comment# 1   - Wade · USA · Dec 20, 2012 @ 11:17am

The original plan was to harvest the agae to produce fuel. Harvesting to be done by electro magnets. An area the size of the North Sea would produce enough fuel to proved the transportation needs of the planet perpetually.
   comment# 3   - Gerald Peterson · Mtn. View, HI USA · Dec 21, 2012 @ 12:04am

there is no co2 problem.its all fiction.whats next; charging to exhale? people should stop trying to improve what god created.climate change is not something changes every hour.thats what weather is.up and down tempertures,not constant.
   comment# 4   - gary ligon · omaha,ne.usa · Dec 21, 2012 @ 2:50pm

This is a great news about Geo-Engineering Against Climate Change.
   comment# 5   - Marry · siliguri,India · Mar 23, 2013 @ 1:07am
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