Ocean fertilization

Oceans & marine

The oceans are the largest carbon sink for atmospheric carbon, and have taken up over 30% of anthropogenic emissions. Carbon uptake occurs abiotically through processes like ocean-atmosphere interaction and weathering processes, and biotically, mainly through carbon consuming photosynthesising organisms.

Ocean fertilization schemes seek to increase the amount of available nutrients in the top layer of the ocean to stimulate the growth of phytoplankton. These organisms play a major role in the oceanic carbon cycle as they utilize CO2 when photosynthesising. By encouraging greater bioproductivity, more carbon can be sequestered by organisms in the “biological pump” when they die and sink to the ocean floor and thereby remove carbon from the carbon cycle (Smetacek et al. 2012; Williamson et al. 2012). Such fertilization can also be used to stimulate higher entropic levels, for example fish production in an area (See fish management). Moreover, the UN report on marine Geoengineering speculates that further research might be done into the potential to create albedo enhancing algal blooms, which would directly reflect incoming solar radiation (GESAMP 2019; see also ocean albedo enhancement). Several different fertilization schemes have been suggested. Upwelling shall be discussed in more detail below, here the focus will be on the purposeful distribution of nutrients on the surface. Marine Phytoplankton need nitrogen (N), phosphorus (P), and iron (Fe) to grow, and there have been proposals to use all three of these elements as fertilization material. Most research has focussed on Fe fertilization, and this shall also be the focus of this section. Fe plays a crucial role in ocean biochemistry (Tagliabue et al. 2017), and occurs naturally in the atmosphere and derives from multiple sources. Ito et al. (2021) note there is still large uncertainty about such sources and its role in ocean biochemistry. Although most studies generally conceive distribution from ships, there are alternatives, like the idea to spread very fine iron-containing powder from airplanes (Emerson 2019).

Technological Readiness Level (TRL)

Low 1

The technology is already proven to work locally, as natural analogues and several controversial experiments have shown that the addition of certain particles to the water can cause a localized algae bloom. However, whether this can be efficiently replicated artificially at a larger scale has not yet been proven. Mongin et al. (2021) for example claimed that many fertilizers would sink down before they could be utilized by phytoplankton, and their model study showed that this might reduce potential CO2 uptake by half. There are furthermore questions about the durability of carbon sequestration through the sedimentation of dead biomatter (Fuss et al. 2018). The IPCC AR6 WG3 report assigns it very low technological readiness of 1 to 2 (p116).

Technological Readiness Level (TRL)

A technology with a TRL of 1-3: TRL 1 – Basic; TRL 2 – Concept formulated; TRL 3 – Experimental proof of concept

Scalability

Unknown 0

The National Academies of Sciences report (2022) states that they have ‘medium to high confidence that this approach will be effective and scalable’, and add that the costs to scale up the technology would be relatively low (2021). Spatially, the scaling of specific measures would be limited by the local availability of nutrients, as there are for instance only a few areas that can be said to have a major relative deficiency of iron.

Timeliness for near-future effects

Unknown 0

There are too many uncertainties around this measure to provide a clear answer to this.

Northern + Arctic potential

Unknown 0

It is unclear if this measure would be particularly effective in Northern and Arctic regions, but Iron fertilization could potentially be important as one of the planet's oceans three major iron deficient zones is the subarctic North Pacific (Boyd et al., 2007).

Global potential

Unknown 0

In their 2008 report, the Royal Society estimates that by 2100, ocean fertilization would be able to sequester up to 3.7 GtCO2 per year (Lampitt et al, 2008). The IPCC AR6 WG3 report notes that experimental results show a far lower efficiency than theoretical calculations, and ultimately estimates carbon uptake potential of 1 to 3 Gt CO2 per year. However the GESAMP report on marine geoengineering technologies states that 'degree of enhancement of the biological pump varied considerably between experiments', with findings anywhere between a 50 and 8 percent enhancement (GESAMP, 2019). It furthermore also needs to be clarified how much carbon could be released back into the atmosphere when biomass breaks down and the captured carbon is respirated back to higher oceanic layers, and if increased bioproductivity causes a greater emission of other GHGs like methane (GESAMP, 2019).

Cost - benefit

Unknown 0

The price per tonne of carbon sequestered is still highly uncertain, with a literature review giving the vastly differing $2 to $457/tCO2 (Fuss et al. 2018). The IPCC AR6 wg3 report estimates a cost of 50 to 500 dollars per captured tonne of CO2. In terms of financing, Cooley et al. (2022) find that many ocean CDR techniques 'resonate with existing experiences of greenhouse gas mitigation and, increasingly, terrestrial CDR,' and that this allows such technologies to build on already existing financing frameworks

Environmental risks

Medium 2

The oceans remain largely understudied, and tinkering with lower entropic levels could have major consequences for the entire system and might seriously impact local ecosystems (Boyd et al, 2022; IPCC AR6 WG3, 2022). Fertilization might for example cause environmental damage by causing toxic algae blooms (Wallace et al, 2010; Bertram et al., 2010) and ocean acidification (Williamson and Turley, 2012). The NASEM report thereby attributes a medium level of environmental risk to this measure (2021).

Environmental risks

More widespread and possibly regional impacts that extend beyond the immediate solution deployment location

Community impacts

Unknown 0

If fertilization affects local ecosystems it will also impact dependent local and indigenous communities. This could therefore have positive and negative effects, and issues of climate justice have to be taken into consideration (Batres et al, 2021). If fertilization works as it supposed to, it might for example lead to increased fish stocks (NASEM, 2022), however Wallace et al, (2010) write about the potential for ‘nutrient robbing’, or the possibility 'that fertilization of an open ocean location in international waters could reduce productivity around islands and countries not involved with the fertilization activity'. Cooley et al. (2022) find that the public stance and framing of ocean fertilization and other ocean CDR technologies is crucially important for their future implementation potential.

Ease of reversibility

Unknown 0

Wallace et al (2010) state that even though localized experiments likely did not have permanent effects, it needs to be better understood if larger experiments would also be reversible and not have more permanent effects.

Risk of termination shock

Unknown 0

Legality/governance

Unknown 0

There are many national and regional laws that deal with water pollution. However, many early ocean fertilization experiments took place on open oceans, outside the jurisdiction of individual nation states. After the outrage this caused, several conventions tried to counter uncontrolled polluting of the oceans in this way. The most notable of these initiatives is the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (better known as the London Convention). After it was first amended in 1972, it was modified in 2008 and 2013 in order to regulate ocean fertilization. However, Silverman-Roati et al write ‘[t]here are currently no legally binding international treaties dealing specifically with ocean fertilization’, and ‘[i]n general, the international legal framework for ocean fertilization includes several gaps, and no comprehensive framework governs’ (2022).

Scientific/media attention

High 3

Ocean Fertilization has a relatively long history, with several highly controversial experiments in the 1990s and early 2000s that gained widespread attention, most infamously perhaps when Russ George spread 100 tonnes of iron sulfate into the Pacific Ocean in 2012. In 2021, the organization geoengineeringmonitor claimed that there had been 'at least 16 open ocean fertilization experiments'. There have been large projects like the German-led LOHAFEX, and the Korean KIFES program in the Southern Ocean, as well as major institutionalized research, like at the Cambridge Center for Climate Repair, and the EU’s ongoing reviewing project OceanNETs (www.oceannets.eu/), and NASEM (2021) argued for the consideration of future mesoscale experiments. There are also many commercial companies that are exploring this measure, like Exploring Ocean Iron Solutions (https://oceaniron.org/), and the Australian Ocean Nourishment Corporation (oceannourishment.com), whose WhaleX project received some attention after being shortlisted for Elon Musk's CDR prize (Readfearn, 2021).

Scientific/media attention

Numerous scientific papers with substantial funding and ongoing research groups; significant media attention and "hype"; many companies exploring commercialization options

References

https://www.geoengineeringmonitor.org/wp-content/uploads/2021/04/ocean-fertilization.pdf

Batres, M., Wang, F. M., Buck, H., Kapila, R., Kosar, U., Licker, R., ... & Suarez, V. (2021). Environmental and climate justice and technological carbon removal. The Electricity Journal, 34(7), 107002. https://doi.org/10.1016/j.tej.2021.107002

Bertram, C. (2010). Ocean iron fertilization in the context of the Kyoto protocol and the post-Kyoto process. Energy Policy, 38(2), 1130-1139. https://doi.org/10.1016/j.enpol.2009.10.065

Boyd, P. W., Jickells, T., Law, C. S., Blain, S., Boyle, E. A., Buesseler, K. O., ... & Watson, A. J. (2007). Mesoscale iron enrichment experiments 1993-2005: synthesis and future directions. science, 315(5812), 612-617. http://doi.org/10.1126/science.1131669

Cooley, S. R., Klinsky, S., Morrow, D. R., & Satterfield, T. (2023). Sociotechnical considerations about ocean carbon dioxide removal. Annual Review of Marine Science, 15, 41-66. http://doi.org/10.1146/annurev-marine-032122-113850

Emerson D (2019) Biogenic Iron Dust: A Novel Approach to Ocean Iron Fertilization as a Means of Large Scale Removal of Carbon Dioxide From the Atmosphere. Front. Mar. Sci. 6:22. https://doi.org/10.3389/fmars.2019.00022

Fuss, S., Lamb, W. F., Callaghan, M. W., Hilaire, J., Creutzig, F., Amann, T., ... & Minx, J. C. (2018). Negative emissions—Part 2: Costs, potentials and side effects. Environmental Research Letters, 13(6), 063002. https://doi.org/10.1088/1748-9326/aabf9f

GESAMP (2019). “High level review of a wide range of proposed marine geoengineering techniques”. (Boyd, P.W. and Vivian, C.M.G., eds.). (IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UN Environment/ UNDP/ISA Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection). Rep. Stud. GESAMP No. 98, 144 p. Available at: http://www.gesamp.org/publications/high-level-review-of-a-wide-range-of-proposed-marine-geoengineering-techniques [Accessed 18 July 2024]

Ito, A., Ye, Y., Baldo, C. et al. Ocean fertilization by pyrogenic aerosol iron. npj Clim Atmos Sci 4, 30 (2021). https://doi.org/10.1038/s41612-021-00185-8///Boyd, P.W., Bach, L.T., Hurd, C.L. et al. Potential negative effects of ocean afforestation on offshore ecosystems. Nat Ecol Evol 6, 675–683 (2022). https://doi.org/10.1038/s41559-022-01722-1

Lampitt, R. S., Achterberg, E. P., Anderson, T. R., Hughes, J. A., Iglesias-Rodriguez, M. D., Kelly-Gerreyn, B. A., ... & Yool, A. (2008). Ocean fertilization: a potential means of geoengineering?. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 366(1882), 3919-3945. https://doi.org/10.1098/rsta.2008.0139

Mongin, M., Baird, M. E., Lenton, A., Neill, C., & Akl, J. (2021). Reversing ocean acidification along the Great Barrier Reef using alkalinity injection. Environmental Research Letters, 16(6), 064068. https://doi.org/10.1088/1748-9326/ac002d

Oschlies, A., Koeve, W., Rickels, W., & Rehdanz, K. (2010). Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization. Biogeosciences, 7(12), 4017-4035. https://doi.org/10.5194/bg-7-4017-2010

Readfearn, Graham (23 December 2021). Can fake whale poo experiment net Australian scientists a share of Elon Musk’s US$100m climate prize? The Guardian https://www.theguardian.com/environment/2021/dec/24/can-fake-whale-poo-experiment-net-australian-scientists-a-share-of-elon-musks-us100m-climate-prize

Silverman-Roati, K., Webb, R. M., & Gerrard, M. (2022). Removing Carbon Dioxide Through Ocean Fertilization: Legal Challenges and Opportunities. Available at: https://scholarship.law.columbia.edu/faculty_scholarship/3637

Smetacek, V., Klaas, C., Strass, V. H., Assmy, P., Montresor, M., Cisewski, B., ... & Wolf-Gladrow, D. (2012). Deep carbon export from a Southern Ocean iron-fertilized diatom bloom. Nature, 487(7407), 313-319. https://doi.org/10.1038/nature11229

Tagliabue, A. et al. 2017. The integral role of iron in ocean biogeochemistry. Nature 543, 51–59. https://doi.org/10.1038/nature21058

DWR Wallace, CS Law, PW Boyd, Y Collos, P Croot, K Denman, PJ Lam, U Riebesell, S Takeda, & P Williamson: 2010. Ocean Fertilization. A Scientific Summary for Policy Makers. IOC/UNESCO, Paris (IOC/BRO/2010/2). Available at: https://unesdoc.unesco.org/ark:/48223/pf0000190674 [Accessed 18 July 2024]

Williamson, P., & Turley, C. (2012). Ocean acidification in a geoengineering context. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 370(1974), 4317-4342. https://doi.org/10.1098/rsta.2012.0167

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Land-based measures

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Industry

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Atmosphere / solar radiation

Space-based solar radiation management

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