Future EU Rules on Marine-Based Carbon Removal (mCDR) in discussion in Brussels

Wave from beneath. Jeremy Bishop | Unsplash

European climate officials, scientists and industry experts are gathering this week in Brussels for a technical workshop on marine-based based carbon dioxide removal (mCDR) – also known as ocean-based carbon dioxide removal (oCDR).

PML scientists Professor Helen Findlay and Guy Hooper are attending the event, which comes as the European Commission develops certification methodologies under the EU’s recently adopted Carbon Removals and Carbon Farming Regulation (CRCF) – a framework designed to ensure that emerging carbon removal technologies deliver genuine, lasting climate benefits.

The focus of the discussion will be Direct Ocean Carbon Capture and Storage (DOCCS), a method that manipulates seawater chemistry to extract dissolved carbon from the ocean, allowing the ocean to take up more carbon dioxide from the atmosphere.

The DOCCS process itself is relatively straightforward: electrochemical systems split seawater or brine into acidic and alkaline streams. In the dominant “acid route,” the acid drives CO₂ out of seawater, which is then captured and stored – much like conventional carbon capture and storage but using the ocean as the initial CO₂ source. After extraction, the alkaline stream restores the water’s chemistry before discharge.

The treated, carbon-depleted water must re-equilibrate with the atmosphere, drawing down CO₂ as it mixes through the ocean. This occurs across varying spatial scales – from within metres of the discharge point to potentially hundreds of kilometres as currents disperse the water – and over timescales ranging from weeks to years.

This complexity is precisely why the EU has established its QU.A.L.ITY criteria (Quantification, Additionality, Long-term storage, and Sustainability) – which all certified carbon removals must meet.

The workshop will examine whether DOCCS can satisfy these requirements.

A January 2026 technical review prepared for the Commission by ICF consultants highlights the central challenge: “the carbon extracted to storage in the [DOCCS] process is not the carbon that is removed from the atmosphere and therefore is not directly creditable. Rather it is the corresponding uptake of carbon from the atmosphere as the surface-ocean/atmosphere system re-equilibrates that can be credited as carbon removal.”

PML’s Professor Helen Findlay, a Biological Oceanographer and world-renowned expert on Ocean Acidification, said:

“DOCCS has potential, but there are still many challenges. Verifying the carbon removal is one of those, but we also need to consider safe operation of these technologies, particularly when we get to climate-relevant scales. This workshop is an opportunity to also consider the challenge of potential environmental impacts and how we monitor for those alongside the carbon uptake.”

Guy Hooper, an applied marine scientist with PML whose work (including as part of the SeaCure project which is run jointly by PML and the University of Exeter) has focused on the potential unintended environmental impacts associated with DOCCs, added:

“More evidence is needed on whether DOCCS can generate credible, certifiable carbon removal units. At PML we are continuing to carry out research to better understand the challenges, impacts and limitations of scaling such technologies, and doing so in a way that is both responsible and regulated effectively.”