Schlagwort: ocean alkalinity enhancement

Peer-reviewed Publications

Lee et al. (2026): Ocean Carbon Dioxide Removal and Storage

Chang-Ho Lee, Adam V. Subhas, Ju-Hyoung Kim and Kitack Lee, IN: Chemical Reviews, https://doi.org/10.1021/acs.chemrev.5c00433

Direct observations indicate that the global ocean has a net carbon uptake of 2.6–3.0 petagrams of carbon annually, representing nearly 30% of anthropogenic CO₂ emissions. This review examines two principal domains of oceanic carbon cycling. The first concerns the natural uptake and storage of anthropogenic CO₂, with emphasis on the response of the marine carbonate system and the spatial distribution of absorbed carbon. The second addresses emerging marine CO₂ removal strategies, especially ocean alkalinity enhancement and macroalgae-based approaches.

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Peer-reviewed Publications

Moras et al. (2026): Impacts of water advection and CO₂ exchanges on the carbon dioxide removal potential of ocean alkalinity enhancement

Charly A. Moras, Matias Saez Moreno, Peggy Bartsch, and Jens Hartmann, IN: EGUsphere, https://doi.org/10.5194/egusphere-2025-6144

Ocean alkalinity enhancement is a carbon dioxide removal strategy with high CO₂ uptake potential and rather low cost. Long term modelling studies have focused on this strategy, but most laboratory experiments focus on shorter term with strong advection, which may not be representative of natural systems. Hence, the long-term fate of alkalinity is yet to be addressed. Also, the role of CO₂ ingassing is still largely overlooked. In a new setup, 6-month experiments using solid Ca(OH)₂ and Mg(OH)₂, and liquid NaOH have been conducted with a constant supply of CO₂.

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Peer-reviewed Publications

Tiwary et al. (2026): Simulated Earth system response to acid downwelling as a form of ocean alkalinity enhancement

E Tiwary, M Jürchott and A Oschlies, IN: Environmental Research Letters, https://doi.org/10.1088/1748-9326/ae2105

‘Acid downwelling’ (AD) is a proposed marine carbon dioxide removal (CDR) method, which describes the idea of electrochemically splitting open ocean surface water into an alkaline solution to remain at the surface ocean and cause additional ocean CO₂ uptake, and into an acidic solution that is pumped down into the deep ocean for disposal via vertical pipes. In this study, the authors simulate idealized large-scale AD in an Earth system model of intermediate complexity with different acid injection depths and downwelling intensities.

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Peer-reviewed Publications

Robinson et al. (2025): Nickel extraction from olivine using waste acid from an electrochemical marine CO₂ removal process

Alexander J. Robinson, Dan Thien Nguyen, Brady Anderson, Jian Liu, Pravalika Butreddy, Elias Nakouzi, Qingpu Wang, Paul Marsh and Chinmayee V. Subban, IN: Sustainable Energy & Fuels, https://doi.org/10.1039/d5su00850f

Global production of nickel (Ni) and ferronickel (FeNi) alloys, critical to battery materials and stainless steel alloys, is limited to a few countries due to the distribution of laterite ores. To meet the growing demand, an alternative supply of Ni and FeNi alloys needs to be established. Laterite ores result from olivine (MgₓFe₂−ₓSiO₄) weathering under tropical conditions, making olivine a promising alternative source to consider; however, the lower Ni concentration of olivine makes it less economical. One approach to lowering the process costs is using waste chemical inputs in place of expensive commodity chemicals. In this study the authors evaluate the feasibility of using such waste byproducts generated by a demonstration-scale electrochemical marine carbon dioxide removal system to extract Ni from olivine (0.27 wt% Ni) as FeNi alloy.

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Peer-reviewed Publications

Lu et al. (2025): Process modelling and analysis of ikaite production for atmospheric CO₂ removal through ocean alkalinity enhancement

Xuesong Lu, Rachel Millar, Pranav Toutam, Aidong Yang, Spyros Foteinis, Laura Bastianini, Phil Renforth, Stefan Baltruschat, Jens Hartmann, IN: Chemical Engineering Research and Design, https://doi.org/10.1016/j.cherd.2025.12.028

The production of ikaite, a metastable calcium carbonate hydrate, offers a promising pathway for atmospheric CO₂ removal through ocean alkalinity enhancement. This study explores the feasibility of ikaite production through a three-step process, involving calcite (CaCO₃) dissolution under elevated CO₂ pressure, CO₂ degassing from the calcium carbonate rich solution, and subsequent crystallisation.

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Peer-reviewed Publications

Mack et al. (2025): The scalability and carbon removal potential of ocean alkalinity enhancement

Connor Mack, Ryan Hanna, Daniela Dias and David Victor, IN: ResearchSquare, https://doi.org/10.21203/rs.3.rs-7956805/v1

Most studies on economy-wide deep decarbonization find the need for widespread deployment of carbon dioxide removal (CDR) yet almost none of those studies pay much attention to real-world scalability of such novel technologies. The authors assess the scalability of ocean alkalinity enhancement (OAE), a promising CDR approach.

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Peer-reviewed Publications

Wynn-Edwards et al. (2025): Alkalinity enhancement with sodium hydroxide in coastal ocean waters

Cathryn A. Wynn-Edwards, Wayne D.N. Dillon, John Akl, Craig Neill, Harris J. Anderson, Hui Sheng Lim, Mathieu Mongin and Elizabeth H. Shadwick, IN: Scientific Reports, https://doi.org/10.1038/s41598-025-31606-w

Carbon Dioxide Removal (CDR) is increasingly recognised as essential for achieving net zero emissions to limit the impacts of climate change. Ocean Alkalinity Enhancement (OAE) presents a potentially scalable marine CDR (mCDR) technique. Here the authors report on the first OAE field trial in Australia, conducted at a coastal site in Tasmania using continuous addition of aqueous sodium hydroxide (NaOH). The resulting plume of modified seawater was effectively tracked, and changes in surface carbonate chemistry were quantified using a containerised laboratory.

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Peer-reviewed Publications

Sathyanadh et al. (2025): Efficacy of individual and combined terrestrial and marine carbon dioxide removal

Anusha Sathyanadh, Homa Esfandiari, Timothée Bourgeois, Jörg Schwinger, Tommi Bergman, Antti-Ilari Partanen, Matvey Debolskiy, Miriam Seifert, David Keller and Helene Muri, IN: Environmental Research Letters, https://doi.org/10.1088/1748-9326/ae2af5

Limiting global temperature rise below 2 °C requires significant reduction in greenhouse gas emissions and likely large-scale carbon dioxide removal (CDR). This study assesses the CO₂ sequestration and efficacy of two CDR approaches, Bioenergy with Carbon Capture and Storage (BECCS) and Ocean Alkalinity Enhancement (OAE), applied individually and in combination. Using the Norwegian Earth System Model (NorESM2-LM), simulations were designed to ramp up deployment of BECCS and OAE, to an additional area of 5.2 million km² by 2100 for bioenergy feedstock for BECCS, and a CaO deployment rate of approximately 2.7 Gt/year for OAE within the exclusive economic zones of Europe, the United States and China.

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Peer-reviewed Publications

Sathyanadh et al. (2025): Efficacy of individual and combined terrestrial and marine carbon dioxide removal

Anusha Sathyanadh, Homa Esfandiari, Timothée Bourgeois, Jörg Schwinger, Tommi Bergman, Antti-Ilari Partanen, Matvey Debolskiy, Miriam Seifert, David Keller and Helene Muri, IN: Environmental Research Letters, https://doi.org/10.1088/1748-9326/ae2af5

Limiting global temperature rise below 2°C requires significant reduction in greenhouse gas emissions and likely large-scale carbon dioxide removal (CDR). This study assesses the CO₂ sequestration and efficacy of two CDR approaches, Bioenergy with Carbon Capture and Storage (BECCS) and Ocean Alkalinity Enhancement (OAE), applied individually and in combination. Using the Norwegian Earth System Model (NorESM2-LM), simulations were designed to ramp up deployment of BECCS and OAE, to an additional area of 5.2 million km² by 2100 for bioenergy feedstock for BECCS, and a CaO deployment rate of approximately 2.7 Gt/year for OAE within the exclusive economic zones of Europe, the United States and China.

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Peer-reviewed Publications

Stewart et al. (2025): Assessing the limitations of commercial sensors and models for supporting marine carbon dioxide removal monitoring: a case study

Tristen Stewart, Peter Regier, Kyle E. Hinson, Carolina Torres Sanchez, Quinn Mackay, Nicholas D. Ward and Jessica N. Cross, IN: Frontiers in Climate, https://doi.org/10.3389/fclim.2025.1649723 

Several unknowns remain surrounding marine Carbon Dioxide Removal (mCDR) monitoring, reporting, and verification (MRV) practices and capabilities. Current in-situ sensor technology is limited (primarily pH and pCO₂), requiring calculations and assumptions to estimate changes in carbonate chemistry parameters, including total alkalinity (TA). Considering that cost, energy consumption, and accuracy of commercial sensors can vary by orders of magnitude, understanding how well existing sensors perform in an mCDR context is important for this emerging community. Likewise, documenting sensor limitations and how relatively simple models can optimize sensor deployments will improve MRV efforts and support protocol development. Here the authors (1) compare performance a variety of commercially available sensors in a blind mesocosm experiment simulating ocean alkalinity enhancement (OAE), and how sensor performance impacted carbonate chemistry estimates; (2) evaluate if sensors can distinguish the OAE signal from natural variability during a small scale OAE field test in Sequim Bay, WA, USA, and (3) use an idealized ocean biogeochemistry model to explore optimal sensor network design based on (1) and (2).

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