Assessing the Potential of Seaweed-Based Carbon Dioxide Removal: Scaling Up and Future Evaluation

To meet global climate targets, carbon dioxide removal (CDR) techniques are essential alongside efforts to reduce greenhouse gas emissions. Among marine CDR (mCDR) approaches, the enhancement of the ocean’s role as a natural "blue carbon" sink, particularly through the cultivation of pelagic macroalgae, is gaining increasing attention for its potential to scale carbon sequestration.

For these approaches to be viable and sustainable, they must undergo rigorous evaluation. This study assesses the potential of scaling up seaweed cultivation, considering environmental effectiveness, durability, and risks. It situates this approach within the broader context of other mCDR strategies, including ocean alkalinity enhancement, enhanced coastal weathering, and coastal blue carbon. In addition, the study explores the role of macroalgae in producing products for defossilisation, contributing to the decarbonisation of industries reliant on fossil-derived materials.

In a future step, the Unified Assessment Framework (ASMASYS), a transdisciplinary tool for evaluating marine CDR options, will be applied to assess the feasibility, sustainability, and risks of pelagic macroalgae in the context of global carbon sequestration efforts. This framework integrates scientific, social, legal, and governance factors, emphasizing sustainability and social acceptability.

This work provides an interim synthesis of pelagic macroalgae's potential for large-scale carbon sequestration and defossilisation products. It also lays the foundation for future research, policy recommendations, and governance frameworks necessary for integrating seaweed cultivation into global climate and defossilisation strategies.