GHG-R Flagship Destination

Farming for Blue Carbon
Modeling seaweed cultivation for marine CDR and ocean restoration

Team: Stephen Monismith, Robert Dunbar, Kristen Davis, Ben Saenz

Farming for Blue Carbon: Assessing Seaweed Cultivation for CO₂ Removal - In a 2022 report, the National Academy of Sciences evaluated six marine carbon dioxide removal (CDR) methods and identified seaweed farming as a promising strategy, with potential to scale globally and deliver substantial co-benefits to coastal ecosystems. The remarkable growth and CO₂ uptake rates of seaweeds is sparking excitement in the oceanography community. Seaweeds exhibit high rates of photosynthesis, fixing large amounts of inorganic carbon in the upper ocean while consuming relatively small quantities of nutrients. However, to harvest 1 billion tons of seaweed carbon per year, it may be necessary to farm an area almost twice the size of California. 

To refine our estimates of the carbon sequestration capacity of seaweed, we need to measure the primary carbon flux pathways in field-scale projects, which are scarce. The shortage of data inhibits our ability to develop scientifically rigorous carbon accounting methods and monitoring, reporting, and verification (MRV) protocols. To address these hurdles, we plan to quantify carbon fluxes at an operational kelp farm in Santa Barbara, California. We will observe oceanographic conditions and collect data regarding seaweed biomass and nutrient and carbon system parameters over a growing season. We will quantify carbon flux pathways and identify measurable quantities that allow us to develop MRV protocols for seaweed farms. We will calibrate an existing mechanistic numerical model (MACMODS) of carbon cycling in seaweed farms to estimate the annual carbon sequestration at the kelp farm.