Three challenges to marine carbon dioxide removal

[Geoengineering News]

https://www.nature.com/articles/s44183-026-00198-x

Authors: Victor Brun, Marine Lecerf, Olivia Le Gouvello, Isabella Reis Costa, Chris Bowler, Robert Blasiak, Laurent Bopp, Ken Buesseler, Helen S. Findlay, Jean-Pierre Gattuso, David T. Ho, Lisa A. Levin, Lauren S. Mullineaux, Fabrice Pernet, Hans-O. Pörtner, Yunne-Jai Shin, Robert C. Steenkamp, Torsten Thiele & Joachim Claudet 

21 May 2026

Abstract

Reaching the Paris Agreement target to limit global warming below 1.5 °C requires both decarbonization and the removal of carbon dioxide from the atmosphere. Here, we highlight three challenges to marine carbon dioxide removal (mCDR) (knowledge gaps, ecological and social risks, and inadequate governance), which must be addressed before considering mCDR as a scalable climate solution. Until then, field experiments should remain strictly regulated and limited to advancing scientific understanding.

Source: NPJ

[Michael Hayes]

While awareness of marine Carbon Dioxide Removal (mCDR) remains limited among policymakers and the general public, the technical breadth of mCDR precludes the efficacy of a singular governance model. Existing guidelines for environmental and socioeconomic impact studies and CDR field-level deployment have been established within this field. However, due to the extensive diversity of technologies encompassed, governance assumptions relevant to one mCDR technology often bear no relevance to others. This dynamic frequently leads to a form of opposition that resembles Gish Galloping rather than constructive critique.

Each distinct mCDR technology, or combination of mCDR and mSRM technologies, necessitates tailored governance standards, given the unique characteristics and potential impacts of each.

The development of a highly restrictive, monolithic global governance framework for mCDR, as an overarching domain, is likely to impede the most innovative, sustainable, and socially beneficial mCDR technologies before they can undergo initial field-level evaluations.

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[Greg Rau]

I'm with you , Michael. I was a reviewer of this paper and much of my criticism offered seems to have been ignored. This paper is the latest in a long list that make blanket statements about the uncertainty and risks of all of mCDR methods conducted at any scale (with the glaring exception of Blue Carbon, which for some reason gets a free pass here despite concerns including its irrelevance to global-scale CO2 managment, here).  

 

 We can all agree that before mCDR can be deployed and credited we must establish "....robust monitoring standards (for both MRV and EIA), creating, improving, or integrating international governance frameworks, and ensuring that any deployment is grounded in environmental justice and inclusive public participation".  Yet the paper presumes that such requirements can't be and aren't being responsibly done at small scales already, under existing national governance, MRV, EIA, and social license  (eg, here, here and here). The particular focus on our alleged inability to measure mCDR seems counter to scientists' high-profile reporting of global ocean CO2 uptake to within +/-13% (!, here). Such tools and abilities are indeed allowing anthro-mCDR (and its uncertaities) to be measured and credited at small scales by  private entities (here).  So rather than a blanket, research-only, non-crediting, no-private-sector stance advocated here and elsewhere, what is needed is a more inclusive strategy that allows, in addition to pure research, responsible crediting and private investment when/where justified.

 

As the Earth's CO2 overburden grows, CDR becomes even more essential to ocean and planetary conservation because it is the only way to reduce atmospheric/ocean CO2 on other than geologic time scales once emissions = zero. It is also very risky to assume that all require CDR can be land-based (that is somehow immune to some of the same concerns raised by the authors re mCDR) . mCDR therefore needs to be an all hands on deck effort where innovation and the RDD&D required to determine capacity, cost-effectiveness and safety are encouraged and fostered. That won't happen with a universal R-only focus that will simply continue to unnecessarily stunt progress and ensure that mCDR, despite its huge potential, remains the afterthought it’s always been in global CO2 management and ocean conservation. The ocean and the planet deserve/demand a more inclusive, broadminded approach to CDR and to mCDR in particular, IMHO.

Greg

 

 

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[GRETCHEN & RON LARSON]

Liat, Michael, Greg and ccs

 

    I've only skimmed this article, but think they have not been watching the CDR part of mCdR.  ThatCDR is dominated by biochar.  I suspect mCDR may also be.

 

    This paper identifies 3 categories of mCDR, which cover 6 subcategories.   Three of the six are biological.  My (non-expert) understanding is that all three could serve as home for a biochar approach. "My" AI helper said  f that about 10% of biochar papers could be mCDR.   This should therefore equate to several per month.  Enough that the word "biochar" should have appeared at least once in this paper. 

 

      There is a thriving commercial seaweed industry in China and other parts of Asia.  Problem is that such seaweed is highly valued for food.  Similarly there has always been a strong market for charcoal from mangroves.  Also we hear about biochar being made regularly now from sargasso - a serious threat to tourism in the Carribean.

 

     Also there are quite a few papers interested in HTC (hydrothermal carbonization) - a liquid version of pyrolysis, that overcomes the need for a dry feedstock with biochar's normal use of pyrolysis.   The paper has a table there saying that the three marine biomass CDR products all have short life-times.  True ,but not if the HTC product is further pyrolyzed

 

     I therefore conclude that the warnings of the paper are ill-deserved for at least the biochar communiy.   I predict a healthy future for the biochar portion of mCDR.  Could be a reason for  a needed increased growth of sea grasses (at least the annual varieties)  

 

    But I write this only as an observer.   

 

Ron

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[Michael Hayes]

Ron, your expert level insights regarding biochar, within the general subject of mCDR, may gain significant weight at the AI agent level if reiterated consistently. Most AI data crawlers look for unique combinations of words in expert discussion groups like this group. Also, I appreciate your reminder about HTC; it does present an ideal solution for biochar related mCDR efforts.

Greg, in my first response, I removed a question concerning the disparity in governance frameworks between terrestrial CDR and mCDR, and I thank you for highlighting this glaring dichotomy.

In some ways, I would like to see a seperate mCDR group created just to feed AI data crawlers keywords and concepts found within mCDR, they are still rather uninformed about mCDR. However, I'm also concerned with the level of silo-ing throughout the CDR field. Crossing multiple lines of expertise areas to gain a scalable, sustainable, and governable multiplexed CDR system of systems is likely our best long-term mCDR and CDR bet...and renewable energy bet.

Best regards