To keep global temperatures from increasing by 1.5-2°C within this century, a strong carbon dioxide removal (CDR) strategy that removes ~0.1 Gt CO2 per year from the atmosphere is essential. Short-term CDR approaches can address the immediate need to reduce atmospheric carbon while permanent technologies are developed over the coming decades. One such short-term solution involves cultivating fast-growing macroalgae to capture carbon and sequester macroalgal biomass in the deep ocean. Macroalgae offer significant advantages: they do not rely on arable land, fresh water, or added fertilizers, and high yields can be achieved in offshore areas within the US Exclusive Economic Zone (EEZ). Recent advancements in technology have enabled scalable macroalgal production in these offshore regions, offering the potential to generate industrial scale quantities of carbon-rich biomass for targeted CDR efforts.

Supported by funds from the Advanced Research Project Agency-Energy (ARPA-e), the Valentine research group at UCSB is tasked with developing engineering solutions for biomass conveyance to the deep ocean and study the biogeochemical fate of carbon fixed by macroalgae in smaller scale field and laboratory experiments. Data from these experiments feed biogeochemical models at the global-scale which assess and predict the overall durability of this CDR strategy. Additionally, we aim to evaluate the environmental impacts and risks these activities may pose to ocean ecosystems and the biogeochemical cycles they support. Understanding the processes and durability of macroalgal carbon sequestration will be crucial for designing an effective implementation plan and attracting informed CDR investments.