Carbon removal from the atmosphere requires significant efforts from the science and engineering communities to examine the most efficient solutions and build them up to scale. Seaweed cultivation is considered a potential solution for sequestering CO2, however, the reach of its capabilities globally still needs to be investigated further.
New study was published on June 15th in Communications Earth & Environment that suggests the potential of global seaweed cultivation as a carbon capture solution may not be feasible in the carbon removal range between 2.5 and 13 gigatons of atmospheric carbon per year needed to mitigate climate change. The study is titled: Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints.
The researchers applied a dynamic seaweed growth model that includes growth-limiting mechanisms like nitrate supply, to estimate the global potential yield of four types of seaweed. They also considered various scenarios of nutrient availability and ocean conditions across the global ocean to make the predictions.
The results are showing that harvesting 1 gigaton per year of seaweed carbon would require farming over 1 million km2 of the most productive waters, located in the equatorial Pacific.
Beyond these waters, the cultivation area would need to be tripled to attain that 1 gigaton of sequestration per year. Adding nutrients to maintain seaweed productivity is also important to reach a gigaton scale of CO2 removal via seaweed. Some techniques are “depth cycling” or upswelling nutrients from deeper waters.
The study concludes that to meaningfully assess the carbon removal potential of seaweed cultivation, the global variation in seaweed growth potential “must be understood and future research into the refinement of seaweed farming is needed.”