In this episode, hosts Anna Madlener and Wil Burns are joined by Dr. Grace Andrews and Kristi Weighman of Hourglass Climate — a leading nonprofit researching ocean-based carbon dioxide removal (oCDR, also known as mCDR ) methods like ocean alkalinity enhancement (OAE) — to discuss the launch of the Framework for Ecotoxicological Modeling of mCDR (FEMM). This project explores how ecotoxicological modeling and existing statistical approaches can be applied to OAE and oCDR projects, improving the field’s understanding of these potential climate solutions’ environmental risks. Dr. Andrews and Weighman offer insight into their process building and receiving feedback on FEMM, the framework’s regulatory potential, and how FEMM can be applied across oCDR research. 

Dr. Grace Andrews, Founder and Executive Director of Hourglass Climate, now in her tenth year of working in the CDR field, last appeared on Plan Sea in 2024 to discuss Hourglass’ role in advancing monitoring, verification, and reporting (MRV) for OAE. In this episode, she’s joined by Kristi Weighman, an Hourglass scientist with expertise in ecotoxicology. Together, Grace and Kristi discuss how they recognized a critical gap in oCDR research — the lack of tools to monitor and model environmental risk — and developed a first-of-its-kind framework to fill that gap. 

Grace explains how our understanding of oCDR’s environmental safety has lagged behind scientific developments in the field. In order to advance these projects in a responsible way, Grace believes that the field needs more rigorous, standardized approaches for modeling and measuring environmental risks. 

FEMM aims to address this gap through combining established statistical approaches with emerging modeling techniques, borrowing existing protocols from the ecotoxicology space and applying them to the nuances of oCDR. The framework begins with a screening-level assessment that uses highly conservative assumptions to determine whether a project’s risks can be ruled out. Projects with identified risk may need to redesign aspects of their approach before moving on to more realistic assessment tools. The modeling relies on species sensitivity distributions (SSD) and calculations based on predicted environmental concentration (PEC) and predicted no effect concentration (PNEC). While this SSD approach has been applied to other environmental stressors, this is the first time it’s been applied to oCDR. Grace and Kristi also highlight examples of specific mCDR stressors and conditions where data may be too sparse to fully apply this approach today, and outline research priorities that will enable a standardized approach for these over time.

Looking ahead, Grace and Kristi share their optimism about FEMM’s utility for researchers and broader oCDR stakeholders. They hope the tool will enable users to identify potential risk in their proposed projects, integrate cross-disciplinary data, and foster greater regulatory dialogue. 

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative and the American University Institute for Responsible Carbon Removal.

To listen to Dr. Grace Andrew’s first Plan Sea podcast appearance,

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this episode of Plan Sea, hosts Anna Madlener and Wil Burns sit down with Stefano Capello, CEO and founder of Limenet — an Italian startup focused on limestone-based ocean alkalinity enhancement (OAE) and net-zero lime production — and Sara Groppelli, a PhD researcher at the University of Milano-Bicocca studying the impact of Limenet’s approach on phytoplankton communities. Stefano discusses Limenet's journey from theoretical experiments in his grandmother’s garage to a pilot plant in Italy that is navigating key, real-world questions around cost efficiency and scale, environmental safety, permits and regulatory pathways, and community engagement.

Stefano recounts Limenet’s unconventional beginnings, which started as a prototype research project in his grandmother’s garage, and now operates a pilot facility in southern Italy. Since 2023, Limenet has focused on developing an OAE approach that pre-dissolves limestone alkalinity in reactors and pre-equilibrates seawater with atmospheric CO2 before releasing it back into the ocean. This closed-system approach is designed to reduce scientific uncertainty in alkalinity additions and to minimize risks such as particle sedimentation or unwanted precipitation.

Now, Limenet is focused on addressing key questions about how its OAE approach could be scaled. Stefano shares updates on the company’s journey to reduce the energy intensity of its lime production and the associated costs, and how the team is engaging communities and policymakers as they navigate Italy’s regulatory landscape. 

The ecological safety of Limenet’s OAE approach are also important to thoroughly evaluate, and Sara shares updates from her research on potential impacts on phytoplankton communities. Sara highlights how controlled alkalinity enhancement appears to have limited ecological disruption when carefully designed. However, long-term and site-specific studies are important to thoroughly understand potential impacts and also co-benefits, such as potential buffering against ocean acidification. 

Listen to the full episode to learn more about Limenet’s growth and how the team is approaching important questions around environmental safety, cost and scale, monitoring and evaluation, community engagement, permitting pathways, and more.

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative and the American University Institute for Responsible Carbon Removal. Subscribe on your preferred podcast platform and find the entire series here.

ACRONYMS/CONCEPTS:

• CDR: carbon dioxide removal
• ISO: International Organization for Standardization
• MRV: monitoring, reporting, and verification
• OAE: ocean alkalinity enhancement

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this episode of Plan Sea, hosts Anna Madlener and Wil Burns sit down with researchers Dr. Leila Kittu, Dr. Giulia Faucher, and Dr. Charly Moras to discuss the latest updates from the Ocean Alk-Align consortium’s exploration of ocean alkalinity enhancement’s (OAE) environmental safety and efficiency. Representing expertise from the GEOMAR Helmholtz Centre for Ocean Research and the University of Hamburg, Leila, Giulia, and Charly join Anna and Wil to share valuable insights on what’s needed for monitoring, reporting, and verification (MRV) and environmental safety assessments.

Ocean Alk-Align is dedicated to evaluating the efficacy and durability of carbon uptake and storage;  environmental safety and potential co-benefits; and MRV requirements of various OAE approaches. Leila, Giulia, and Charly discuss how understanding OAE’s efficiency — commonly measured by how many tons of carbon dioxide is removed per ton of material added to the ocean — is incredibly nuanced. The group’s research suggests we must also consider factors such as dilution, sinking, and horizontal mixing when discussing the efficiency of various OAE approaches in different real-world settings.

To evaluate OAE’s environmental safety and better understand how scientists can protect living ecosystems without sacrificing efficiency, Leila, Giulia, and Charly discuss mesocosm experiments that were conducted. The team gradually included multiple species of plankton to identify how biological life responds to seawater changes. Mesocosm research is advantageous for breaking down complex problems into manageable pieces — but is limited in terms of scale, duration, and ability to capture higher trophic levels.

Looking ahead, the group called for more robust frameworks for environmental safety assessment and thresholds as OAE projects move towards field research. The group argues that the broader benefit of carbon removal seeks to outweigh the potential risk of interfering in delicate ocean environments, and requires careful consideration and standardization across these frameworks. Ocean Alk-Align’s work aims to provide a scientifically-rigorous, informed pathway to weighing this “give and take” decision.

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative and the American University Institute for Responsible Carbon Removal.

ACRONYMS/CONCEPTS:

• OAE: ocean alkalinity enhancement
• MRV: monitoring, reporting, and verification
• mCDR: marine carbon dioxide removal
• OAE-PIIP: Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this episode of Plan Sea, hosts Anna Madlener and Wil Burns sit down with Dr. Phil Renforth and Dr. Mijndert Van der Spek of Heriot-Watt University to unpack their newly published, harmonized framework for evaluating the viability of ocean alkalinity enhancement (OAE) pathways. Moving beyond lab-scale assumptions, their approach integrates techno-economic analysis (TEA) and lifecycle assessment  (LCA) to allow the exploration of 54 known OAE variations and how they perform under future, decarbonized energy scenarios. The conversation highlights why real-world data, a cleaner energy grid, and feasibility assessments are important for determining which OAE pathways will deliver results in global scale carbon removal. 

With any emerging solution, both feasibility and cost must be effectively evaluated. Renforth and Van der Spek combine two essential lenses – techno-economic analysis (TEA) and lifecycle assessment (LCA) – to build a comprehensive picture of OAE’s real potential. TEA determines if a pathway is economically viable and scalable, while LCA screens for its full environmental impacts, not only if it is net-negative, but also whether it engages in “burden shifting,” or solving one problem while creating another. Operating far beyond “carbon balancing,” LCA works across a range of categories, from greenhouse gas emissions to terrestrial and marine acidification, resource use, and pollution. Together, the two tools are meant to provide a level of quantification for decision-makers investigating the viability of any CDR approach. 

In looking at the framework, Dr. Renforth and Dr. Van der Spek began by introducing  the framework’s structure through a case study of BPMD and its functionality as OAE technology. Rather than offering predictions, the framework helps to show how different technologies perform under current assumptions. This means the framework should not be viewed as forecasting long-term outcomes on its own, but instead as a tool to see how each pathway changes. 

While these tools are powerful, they are incomplete and alongside rigorous research into the broader social, regulatory, and ethical implications of each potential pathway. For example, LCA aims to measure global stressors by normalizing impacts, but it does not have the ability to detect localized effects. This highlights that any comparison drawn from the framework must be paired with site-specific environmental assessments. Together, these layers of analysis provide a more realistic understanding of where OAE pathways may be within reach. 

Join us as we dive deeper into this framework and how it aims to spur further evaluation and innovation in OAE by listening to the episode above! Subscribe on your preferred podcast platform and find the entire series here. 

ACRONYMS / CONCEPTS:

• CDR: Carbon Dioxide Removal
• OAE: ocean alkalinity enhancement 
• TEA: Techno-Economic Analysis
• LCA: Lifecycle Assessment
• BPMED: Bipolar Membrane Electrodialysis

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this episode of Plan Sea, hosts Anna Madlener and Wil Burns dive deep into the new Biogeosciences special issue focused on the environmental safety of ocean alkalinity enhancement (OAE). This episode’s guests are Dr.Lydia Kapsenberg and Dr. Tyler Cyronak who helped edit the special issue. Compiling more than 20 studies, the special issue serves as a “one-stop shop” of the latest peer-reviewed science on the environmental safety of OAE — ranging from responses of micro algae and corals, to the influence of biogeochemical cycling and trace metals. Tune in as we unpack what insights these studies collectively suggest and discuss what it means for next steps in environmental safety research for OAE. 

The volume of OAE research has grown dramatically in recent years — increasing four-fold over the last five years. The Biogeosciences special issue shines a light on this rapidly evolving landscape and offers a tool for researchers, funders, regulators, and other partners to access centralized information on potential ecological risks, environmental monitoring standards, and feedstock safety related to multiple OAE approaches. 

Throughout the discussion, many themes arise, including the question: How important is it to understand both system-wide patterns and local ecological realities? Lydia and Tyler highlight that while the Biogeosciences studies suggest that many phytoplankton species appear to be resilient under expected OAE conditions, local species and ecological contexts must still be factored into any field research design. This is where researchers have an important responsibility to meaningfully engage with communities on what matters most for their local marine ecosystems and align planned environmental monitoring efforts accordingly.

For researchers, policymakers, and communities assessing OAE’s environmental safety as a potential climate solution, the Biogeosciences special issue offers a crucial early evidence base and a clearer picture of what questions come next.

As mentioned during the episode, Carbon to Sea’s Environmental Impact Monitoring Framework is now available for public review and comment here, through December 12th. Carbon to Sea and the Prince Albert II of Monaco Foundation are also currently soliciting proposals for scientific research on the safety of OAE on commercially and culturally valued marine species. You can view the full funding opportunity and submit a proposal by January 16, 2026.

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative and the American University Institute for Responsible Carbon Removal.


ACRONYMS / CONCEPTS:

• CDR: Carbon Dioxide Removal
• EPA: Environmental Protection Agency 
• MRV: monitoring, reporting, and verification
• OAE: ocean alkalinity enhancement
• OAEPIIP: Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this edition of Plan Sea, hosts Anna Madlener and Wil Burns kick off season three of the podcast with Woods Hole Oceanographic Institution (WHOI) researchers Dr. Adam Subhas and Jennie Rheuban to discuss the LOC-NESS project — a small-scale, open-ocean research trial on ocean alkalinity enhancement (OAE). The project’s co-principal investigators join Anna and Wil to recount the process of receiving a first-of-its-kind permit from the U.S. Environmental Protection Agency (EPA), the role of local community engagement, and the project’s early findings. 

A few weeks ago, WHOI completed its highly controlled research trial in the Gulf of Maine to study the environmental safety and efficacy of OAE as a carbon dioxide removal technique. Approved by the EPA after a two-year, rigorous permitting process, the LOC-NESS project introduced small amounts of purified sodium hydroxide – a compound often used to balance the pH of drinking water – to the ocean surface waters, along with a harmless red dye to help track it. This field study came after years of preparation and development, including extensive laboratory experiments, ocean modeling, and a growing body of scientific literature. 

Dr. Adam Subhas is an Associate Scientist at WHOI and the project lead for LOC-NESS. Adam credits the project’s success so far to the comprehensive preparation and collaboration between WHOI scientists and EPA staff — on everything from ocean modeling and biogeochemical impact evaluation, to engaging communities and local industries on what to expect from the research. He also talks about how their pursuit of the first-ever ocean carbon dioxide removal (oCDR) permit under the Marine Protection, Research, and Sanctuaries Act of 1972, helped the LOC-NESS team refine their procedures, improve their approach, and make the project more responsive to feedback from their community.

Jennie Rheuban is a WHOI Research Specialist and serves as a co-principal investigator for LOC-NESS. Jennie points to community engagement as a critical component of LOC-NESS’s development, recounting the project’s years-long effort to engage with questions from a range of stakeholders, including the fishing community. By emphasizing its position as an independent scientific research project without commercial ambitions, WHOI was able to cultivate credibility and gather important community inputs that shaped the scope and methodologies of the research. For example, the team spent additional time researching types of fish larvae in potential field trial regions to bring that information back to the local fisherman.

Looking ahead, LOC-NESS researchers will continue to analyze data gathered during this summer’s trial to understand the impacts and efficacy of the alkalinity dispersal. 

More information about LOC-NESS’s findings will be shared at the Ocean Sciences Meeting in February 2026.

Plan Sea is a semi-weekly podcast exploring ocean-based solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal. 

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this edition of Plan Sea, co-host Anna Madlener sits down with co-host (and one of this week’s guests) Wil Burns, Dr. Terre Satterfield from the University of British Columbia, and Dr. Chris Pearce from the UK’s National Oceanography Center. Burns, Satterfield, and Pearce are some of the lead authors on a new  report launched at the 2025 UN Ocean Conference, “Principles for Responsible and Effective Marine CDR Development and Governance.”

Commissioned by the High-Level Panel for a Sustainable Ocean Economy, the report outlines how to responsibly evaluate and potentially scale ocean-based carbon dioxide removal (oCDR) — also referred to as marine CDR — along three pillars: scientific and technological readiness, governance, and national implementation. The framework reflects months of collaborative research to help address how oCDR can begin to move from lab trials to real-world deployment — while maintaining high standards of scientific rigor, environmental protection, and public trust. Read the full report HERE.

Dr. Terre Satterfield, Professor of Culture, Risk and the Environment at the University of British Columbia, joins Wil and Anna to discuss the report’s recommendations for national strategies that can accelerate oCDR research and public engagement. She spoke about the importance of streamlining permitting processes for oCDR field trials, earmarking funding for lab networks for holistic oCDR evaluation, and investing in public engagement hubs to help co-design research efforts. 

Dr. Christopher Pearce, drawing from his research on oCDR science at the UK’s National Oceanography Center, discusses how the report offers six categories to assess scientific and technological readiness for various oCDR approaches. This aims to help policymakers better understand when and why, for example, an approach may be quite well-understood by scientists in the lab, but the environmental impacts associated with larger projects are less understood and require field trials for further evaluation. He also explains how tools like pre-permitted testbed sites and national lab networks can promote data sharing and create the infrastructure needed for safe and scalable mCDR projects. 

Looking ahead, Wil, Terre, and Chris discuss how international frameworks like BBNJ (Biodiversity Beyond National Jurisdiction) can ensure accountability for future mCDR governance, and reflect on the major challenges facing the field—from limited public awareness and funding to the need for strong public oversight as the technology scales. The report offers important recommendations, such as creating pre-permitted testbed sites and national lab networks that can promote research efficiency and strong standards as oCDR continues to be evaluated, regulated, and tested. 

To learn more about the report’s findings, listen to the full episode HERE, subscribe with your favorite podcast service, or find the entire series here. 

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

ACRONYMS / CONCEPTS:

• MRV (1:26); Monitoring, Reporting, and Verification
• TRL (6:58); Technology Readiness Level
• SRL (6:44); Scientific Readiness Level
• BBNJ (38:03); Agreement on Biodiversity of Areas Beyond National Jurisdiction, also known a

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this edition of Plan Sea, hosts Anna Madlener and Wil Burns sit down with Kyla Westphal and Dr. Mallory Ringham from Ebb Carbon to discuss Project Macoma — the company’s pilot ocean alkalinity enhancement (OAE) study being conducted in Port Angeles, Washington this summer. A first-of-its-kind endeavor, Project Macoma aims to remove up to 1,000 tonnes of  CO2 from the atmosphere using Ebb Carbon’s electrochemical OAE technology. Kyla and Mallory join to share more about their journey engaging the local community on this proposed research, securing a permit from the U.S. Environmental Protection Agency (EPA), and establishing Monitoring, Reporting, and Verification (MRV) standards as this work gets underway. 

Project Macoma continues the work of the late Dr. Matthew Eisaman, Co-Founder of Ebb Carbon and a pivotal figure in the ocean-based carbon dioxide removal (oCDR) field. Matt dedicated his life to fostering a clear understanding of the scientific path forward for potential oCDR solutions, while also creating an inclusive and environmentally-responsible sector. For more background into Ebb Carbon and a deep dive into their approach, listen to our episode with Matt HERE. 

Kyla Westphal, Vice President of External Affairs at Ebb Carbon, joins Anna and Will to discuss her role developing safe and responsible deployment of OAE. Building on her experience working in what she calls “the intersection between technology and humanity,” Kyla oversees both the stakeholder engagement and ecological safety aspects of Ebb Carbon’s work. She shares how Project Macoma is building on years of foundational environmental research and engagement with Washington state regulators, community groups, and tribal governments to earn local buy-in and support. 

Mallory Ringham, Lead Oceanographer and Head of MRV, then discusses how Ebb Carbon secured the first-ever National Pollutant Discharge Elimination System (NPDES) approval for oCDR under the Clean Water Act. She shares how the permit requires a slow, careful, and continuously monitored operation to ensure water quality standards are met within prescribed mixing zones. Mallory also discusses how Ebb’s foundational research created a strong understanding of the seasonal and tidal variability in the region, allowing for more accurate monitoring and analysis of the project. This summer, Mallory will continue to oversee the monitoring process to ensure the project is operating safely, responsibly, and effectively.

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

ACRONYMS / CONCEPTS:

• MRV (1:05); Monitoring, Reporting and Verification
• NPDES (14:56); National Pollutant Discharge Elimination System
• MCDR; Marine Carbon Dioxide Removal  (21:58)

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

In this edition of Plan Sea, host Anna Madlener is joined by Na’im Merchant, host of The Carbon Curve podcast and Executive Director of Carbon Removal Canada, for a special co-hosted episode of the two podcasts. Recorded live at the Carbon to Sea 2025 Annual Convening, Anna and Na’im speak with Lennart Bach, Associate Professor and ocean alkalinity enhancement (OAE) scientist at the University of Tasmania, to share insights and key takeaways from this year’s convening.

Last month, Carbon to Sea hosted its third Annual Convening in Washington, D.C., bringing together scientists, entrepreneurs, and policymakers to share recent progress and discuss a path forward for OAE. Bach, who previously spoke with Plan Sea on his work in ocean iron fertilization, was a speaker on this year’s “Scientific Research Progress and Updates” panel. Focused on the environmental impacts of OAE, Bach’s research aims to learn more about how OAE approaches may impact the marine ecosystem.

Building on conversations from the convening, Bach joins Anna and Na’im to share his optimism about the future of OAE, while also recognizing the potential challenges posed by a dip in the “hype cycle” that emerging scientific fields often face. However, Bach said he feels confident in progress that’s already been made and noted the importance of building on preliminary findings about OAE’s potential to conduct more targeted research. 

Na’im similarly addresses this challenging moment for the climate industry writ large, as it faces reduced funding and policy support in many areas, with new geopolitical headwinds. Drawing on his experience working across the carbon removal space, Na’im offers advice for how the OAE field can address this moment by prioritizing focused research, establishing an updated roadmap, and exploring new funding pathways. 

Looking ahead, both Na’im and Bach highlight the importance of aligning on MRV approaches, cross-sector partnerships, increased community and policymaker engagement, and exploring new funding pathways in order to advance OAE research. As this year’s convening exemplified, the immediate opportunities in OAE research have largely been addressed; what lies ahead is more complex and demands significantly greater coordination.

Listen to our previous episode with Lennart Bach here.

ACRONYMS / CONCEPTS: 

• OAE (2:28)
• MRV (18:06)
• DAC (23:37)
• CRCF (29:59)
• ETS (29:59)
• ERW (36:16)

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.

This episode of Plan Sea was recorded live at the Ocean Visions Biennial Summit 2025, and features conversations with experts from Ocean Visions, UArctic, and WHOI to discuss their work in the ocean-climate nexus. Host Anna Madlener is joined again by special co-host, Danny Gawlowski, Carbon to Sea’s Senior Manager of Communications and Policy. Listen to Part One of Plan Sea’s coverage of the Ocean Vision Biennial here.

Guests on this episode include: 

• Nikhil Neelakantan, Senior Program Officer at Ocean Visions
• Marianne Hagen, Co-lead of Seabed Curtain Project at UArctic Frozen Arctic Conservation Network
• Kilaparti (Rama) Ramakrishna, Director of Marine Policy Center and Senior Advisor to the President on Ocean and Climate Policy at Woods Hole Oceanographic Institution
• David Koweek, Chief Scientist at Ocean Visions

Plan Sea is a semi-weekly podcast exploring ocean-based climate solutions, brought to you by the Carbon to Sea Initiative & the American University Institute for Responsible Carbon Removal.