Removing CO₂ from the atmosphere? The promises of marine Carbon Dioxide Removal
With COP30 recently taking place in Brazil, the question of how to tackle climate change is on everyone’s mind. Reducing CO₂ emissions is no longer enough to reach the +1.5°C scenario. In recent years, there has been increasing research into the potential of marine Carbone Dioxide Removal (mCDR) mCDR to help achieve climate targets. Together with Dr Miranda Böttcher, researchers at the Copernicus Institute of Sustainable Development are exploring the potential of mCDR—from its underlying theory to its real-world applicability. This topic will also be addressed in a symposium on symposium on Tuesday 25th November.
What is marine Carbon Dioxide Removal?
Marine Carbon Dioxide Removal (mCDR) has been theorized since the early 1990s. It stems from the observation that iron is often a limiting nutrient in the ocean. By adding iron to seawater, the production of photosynthesizing organisms could be enhanced, leading to greater CO₂ absorption and higher O₂ release.
While this initial idea proved to be inefficient, the concept of enhancing the ocean‘s biogenic carbon pump persisted. Planting or expanding kelp forests, mangroves, or seagrass meadows is now being investigated as an alternative. These processes are known as biotic carbon dioxide removal (biotic CDR).
Abiotic carbon dioxide removal (abiotic CDR) is a more recent set of approaches. They involve altering seawater chemistry to amplify the natural processes through which atmospheric CO₂ is absorbed by the ocean.
“Of these two sets of options, biotic CDR has been the most explored,” explains Miranda Böttcher, “and is possibly the closest to being implemented.”
How close are we to implementing mCDR?
In short… not very close. Many issues remain to be addressed before mCDR can be implemented efficiently, safely and justly. From socio-economic and cultural impacts to long-term ecological effects, the challenges posed by mCDR are multifaceted.
“Some communities have a very close relationship with the ocean, and this could affect that relationship,” Böttcher notes. Indeed, past mCDR efforts faced backlash from communities, fisheries, and stakeholders who were unhappy with lack of public engagement and provision of information about the potential unforeseen consequences of trials.
What have we learned through mCDR?
Since it was first proposed, mCDR has been seen alternatively as a promising solution and a dangerous, poorly calculated risk. However, as forest expansion continues to fall short of offsetting global CO₂ emissions, mCDR is increasingly viewed as a potential alternative. To avoid repeating past mistakes, the recent European Marine Board publication calls for close monitoring and stronger regulation.
If anything, research into mCDR has brought unique challenges to light. These solutions require a global perspective and a wide range of considerations. Seas and oceans are interconnected, and actions taken in one region can affect distant ecosystems. Moreover, every culture has a unique relationship with the ocean—one that deserves respect. For mCDR to be implemented effectively, safely and equitably, it requires shared understanding and trust on a global scale.