by Andy Ferguson
Climate engineering (also called “geoengineering”) schemes are not wildly popular with climate activists, and for good reason. These schemes include proposals to dampen global warming by shading the earth, or sequestering carbon using some odd, unproven, and possibly dangerous techniques. If you think that injecting sulphate particles into the upper atmosphere to shade the planet is wack, then you’ll agree with much popular and scientific opinion about why such schemes should mostly be avoided. A few, like reforestation, make sense. But for many others, fossil fuel interests can seize upon such ideas to falsely claim that they can take the place of radical green house gas emission reductions. Responsible scientists and the thinking public completely reject that possibility.
Iron fertilization of the ocean is a geoengineering idea that once seemed promising. Adding relatively small amounts of iron dust to the ocean can cause massive algal blooms that in turn serve as food for tiny fish and other ocean creatures. A huge increase in biological activity can result. Some scientists thought this activity would lead to much CO2 and carbon being captured by sea life and then “exported” to thousands of years of safe storage on the deep sea bottom in the form of fish feces and decayed organisms. Another great benefit was that this process would remove carbonic acid from the ocean, preventing the looming acidification and destruction of ocean ecosystems caused by CO2 emissions. This method of controlling warming and ocean acidification was deemed so simple and cheap that the oceanologist John Martin once famously quipped, “”Give me a half a tanker of iron and I’ll give you the next ice age!” Trouble is, several experiments to test this hypotheses did not show that adding iron to the ocean would have the desired effect of exporting carbon to the sea floor. Some possibly negative effects were observed, and so scientists have backed away from ocean iron fertilization en masse. But in an attempt to sell dubious “carbon offsets,” private businesses began dumping iron into the ocean without supervision or regulation. This resulted in fierce criticism of the practice and ultimately to such commercial activity being abandoned. (Oddly, however, a private businessman spread a ship full of iron particles onto the ocean waters off the coast of British Columbia in 2012 and the resulting massive plankton bloom appears to have led to record salmon runs in western Canadian rivers-but that’s fodder for a different blog).
Whether or not iron fertilization has a positive effect on fisheries and/or climate, another type of “ocean nourishment” scheme worthy of attention has been lost among the ocean fertilization political battles and arguments. According to scientists at the University of Sidney in Australia, adding nitrogen to the ocean should be a much better way to both increase biological activity and export carbon to the sea floor.
Scientists know that adding nitrogen to the ocean provides fertilization and algal photosynthesis in much the same way that adding nitrogen to the soil increases plant growth. What has been little understood is whether adding nitrogen to the ocean is an efficient carbon sequestration strategy. Also, would doing so entail big risks?
Writing in the Journal of Global Warming (1), Martin W. Lawrence of the School of Geosciences at the University of Sidney claims that the rate of carbon sequestration through ocean nitrogen fertilization results in as much as 75% of the resulting photosynthesized carbon being sequestered for immensely long periods of time. This contrasts very favorably with using iron. Studies by Daniel P. Harrison of the Ocean Nourishment Foundation of Glebe, NSW,(2) indicate that iron fertilization results in at best only a few percent of the photosynthesized carbon being successfully exported to the sea bottom. But nitrogen’s behavior as a nutrient is fundamentally different from iron because it naturally recycles itself through the ocean’s biologically active layers until nearly all of it is combined with carbon and exported. In contrast, iron exits those areas fairly quickly and so must be regularly reapplied.
The principle argument against ocean fertilization (or “nourishment”) is the fear that excessive nutrients in one locale can result in eutrofication, meaning zones where algae becomes concentrated and absorbs the available oxygen, killing other sea life. Such zones already exist near the mouths of some major rivers and other areas off the coasts of the USA. In those places, the run off of nitrogen fertilizers and other agricultural chemicals is believed to cause “dead zones” in the ocean. However, nitrogen supporters point out that these effects are easily understood and can be accounted for, so that the right amount of nitrogen nutrients can be added to where it is most needed and useful. Seventy percent of the ocean is nitrogen deficient, and careful application in such areas runs little risk of creating dead zones. Furthermore, the entire process of nitrogen fertilization can be monitored and controlled according to clear milestones to ensure safety. Importantly, no other geoengineering technique appears to offer a direct remedy for ocean acidification, a problem expected to increase for centuries to come due to CO2 emissions already in the atmosphere.
Dr. Lawrence’s paper details the most useful forms of nitrogen, methods of application, and the related costs of applying this nutrient to the ocean. It projects the rate of absorption of atmospheric carbon that would result from this technique, and examines other known risks. The take away is that ocean nourishment with nitrogen should entail far greater benefits and far less risk than many other of the geoengineering schemes now under consideration. Adopted on a wide but clearly affordable scale, this strategy could be an important part of the solution to the problem of ocean acidification, and should help in the fight against CO2 emissions as well. Yet, this technique would only mitigate a small fraction of growing atmospheric carbon emissions. Thus, radical reduction of CO2 emissions must remain the primary and urgent strategy to fight global warming, with ocean nourishment playing at best a complementary role.
Writing in the Handbook of Microalgal Culture (2) Daniel Harrison and his colleague Ian S.F. Jones of U. of Sidney point to other likely advantages of nitrogen fertilization. Increased fish catches could offer a very significant source of income and protein to artisanal fishermen in the coastal regions of developing countries. This is not a trivial bi-product of the nitrogen nourishment scheme, since climate change threatens serious food shortages to wide areas of the planet in the coming decades.
In short, while geoengineering schemes are generally fraught with uncertainty, nitrogen nourishment of the ocean may ultimately be a useful and effective tool in the fight against ocean acidification, plus play a small but significant role in reducing CO2 in the atmosphere. Some may argue that we shouldn’t mess with the oceans because we’ve done enough damage to them already. From my perspective, we’ve already turned the oceans into places of virtually uncontrolled and devastating exploitation. Reducing green house gases is the main battle we must fight, but inaction on ocean nourishment may leave the seas vulnerable to the horrible fate of widespread species extinctions. Ocean nourishment with nitrogen deserves focused attention, worldwide regulation, and larger scale research.
(1) Lawrence, Martin L. “Efficiency of Carbon Sequestration by Added Reactive Nitrogen in Ocean Fertilization” (2014) Int. J. Global Warming, Vol. 6, No. 1 pp 15-31
(2) Jones, Ian S.F., Harrison, Daniel P. “The Enhancement of Marine Productivity for Climate Stabilization” (2013) Food Security Handbook of Microalgal Culture: Applied Phycology and Biotechnology, Second Edition. Chapter 37. Edited by Amos Richmond and Qiang Hu. John Wiley & Sons, Ltd. Published by Blackwell Publishing Ltd.