Ocean fertilization could enhance atmospheric CO2 removal by increasing biological productivity, namely by stimulating the growth of
# Ocean Iron Fertilization: A Promising Path for Carbon Removal? As a marine radiochemist and the director of the non-profit Exploring Ocean Iron Solutions (ExOIS), Dr. Buesseler shared insights on how adding small amounts of iron to the ocean could amplify its natural ability to store carbon, the potential impacts on marine ecosystems, and the path toward responsible research. When scientists compared different climate models' predictions of natural carbon flux in the ocean, the estimates ranged from 5 to 12 billion tons per year. Every marine carbon dioxide removal approach, whether it involves adding minerals, growing seaweed, or fertilizing with iron, will change ocean conditions. We need roughly 5 to 10 billion tons per year of carbon dioxide removal alongside dramatic emissions reductions to address climate change. Ocean iron fertilization might contribute 1 to 2 billion tons annually if deployed widely, though much more research is needed to confirm these estimates and assess full-scale impacts.
Ocean-based carbon dioxide removal (ocean CDR) via nutrient fertilization refers to the addition of micronutrients (e.g., iron [Fe]) and/or macronutrients
Iron fertilization is a Carbon Dioxide Removal (CDR) technique that would artificially add iron to the ocean’s surface to stimulate growth of phytoplankton. When the plume of dust or ash settles over the ocean’s surface, it triggers massive blooms of phytoplankton that remove substantial amounts of carbon dioxide from the atmosphere. Iron fertilization is a Carbon Dioxide Removal (CDR) technique that would mimic this natural system, artificially adding iron to the ocean’s surface to stimulate growth of phytoplankton. If relatively small amounts of iron can be added to the ocean’s surface to effectively remove large amounts of carbon dioxide from the atmosphere, iron fertilization has the potential to play a pivotal role in reducing additional impacts associated with climate change. Until experiments are done to test these potential outcomes and determine how much carbon can be sequestered in the ocean depths, iron fertilization should not be put to use as a method of slowing climate change. ### Fertilizing the Ocean with Iron.
Nutrients like iron can be added to the ocean to spur phytoplankton growth, a process called ocean fertilization. Phytoplankton take up carbon
https://energyfuturesinitiative.org/efi-reports Best guess drawdown potential* Environmental impacts Cost considerations • Moderate to High: 1 to >5 Gt CO2 per year • Space is not limited for offshore cultivation • Pathways for biomass use are underdeveloped • Co-benefit of boosting seafood production and potentially local biodiversity • Nutrient competition with the local ecosystem • Risk of material loss, entanglement of marine life • Biosecurity risks (disease, genetic mixing, invasive species) • Moderate: $25-$125 per ton CO2 removed • New infrastructure required for offshore environment • CDR products and economies of scale do not currently exist ClimateWorks Foundation Artificial Upwelling: Moderate CDR potential despite many uncertainties, but could have important co-benefits for seafood production Ocean Sequestration 17 Best guess drawdown potential Environmental impacts Cost considerations • Moderate: 1 to 5 Gt CO2 per year • Field trial show boost in phytoplankton blooms but carbon drawdown remains uncertain • Upwelling also releases CO2 to the atmosphere • Low to Moderate: <$125 per ton CO2 removed • Highly dependent on pumping methods, operational costs, and monitoring needs Source: www.OceanCDR.net; EFI 2020.
DEEP-OCEAN STEWARDSHIP INITIATIVE Fig. 1 Elements of the biological pump (Fig. 1 From McClain (2010) American Scientist) Deep Ocean Climate Intervention Impacts Deep Ocean Climate Intervention Impacts Ocean Fertilization Key Points DECEMBER 2021 Policy Brief Page 2 DOSI Scaling and Effectiveness The subarctic Northern Pacific, Eastern Equatorial Pacific and Southern Ocean are high-nutrient, low-chlorophyll regions where iron scarcity limits phytoplankton growth, and thus have been proposed for OIF (Yoon et al., 2018, GESAMP, 2019). The alteration of natural phytoplankton communities may result in changes in the seasonality of particulate organic carbon flux to the deep-sea floor (benthic-pelagic coupling) and in compositions of phytoplankton species in the marine snow, potentially impacting deep-sea benthic communities that rely on food from the ocean surface (Billet et al., 1983; Gooday, 1988; Graf, 1989; Ruhl and Smith, 2004; Nomaki et al., 2021).
### The Ocean as a Part of the Climate Solution: Marine Carbon Dioxide Removal (mCDR). The sheer scale of the ocean also means that any marine carbon dioxide removal solutions proven to be viable and safe have the potential to go to the scale needed. Ocean Based Carbon Dioxide Removal. Ocean-Based Carbon Dioxide Removal © 2023 by Ocean Visions is licensed under CC BY-NC-ND 4.0. * Electrochemical Ocean Carbon Dioxide Removal. ### Road Maps to Accelerate the Testing and Development of Marine-Based Carbon Dioxide Removal. The road maps are focused on electrochemical CDR, microalgae cultivation and carbon sequestration, blue carbon restoration and carbon sequestration, macroalgae cultivation and carbon sequestration, and ocean alkalinity enhancement. There has been a great deal of debate about the potential contributions of marine carbon removal techniques to help blunt the ocean-climate crisis, but the reality is these discussions are occurring in an environment of very limited field data. ### Core Principles Guiding Ocean Visions' Work on Carbon Dioxide Removal and the Ocean.