The state of macroalgae carbon dioxide removal: insights from a methodology development team

In the face of anthropogenic climate change, there is strong impetus to develop and implement durable carbon dioxide removal (CDR) technologies, alongside emissions reductions. CDR is an emerging private sector industry seeking to provide scientifically rigorous carbon offsets for entities unable to reduce carbon emissions below regulatory compliance or to support voluntary claims of carbon neutrality and reduction. Among nature-based CDR strategies, macroalgae (seaweed) cultivation is frequently cited as a promising and emerging pathway for ocean carbon storage in a variety of contexts. Despite widespread discussion in the literature and numerous papers that have modeled successful long-term storage by macroalgae cultivation, few field-scale studies exist and no accepted carbon crediting framework exists. Recently, a joint industry-academic partnership attempted to develop a rigorous ecologically-sound carbon credit methodology that aligned the goals of private sector and academic interests in macroalgae CDR. This perspective piece discusses the story of this endeavor, outlining the fundamental science necessary for developing a methodology, challenges that ultimately prevented the team’s completion, and insights into the necessary steps for advancing macroalgae CDR further. Rigorous and scalable macroalgae CDR will likely require public-led investment, greater reliance on affordable monitoring and measurements (e.g., satellite-based remote sensing), and rapid advances in computational processing likely facilitated by artificial intelligence. It is our hope that this perspective on our lessons learned can help inform and better steer the emerging CDR industry and provide a starting point for the next entity that seeks to pursue macroalgae-based CDR, including building on our most recent draft methodology.