# Phytoplankton as CO\({}_{2}\) Sinks: Redirecting the Carbon Cycle
## 5 Discussion  
This is the first study that evaluates the multiple challenges associated with implementing phytoplankton CO\({}_{2}\) sinks globally from a gross number perspective. Other studies have extensively explored relevant aspects of microalgae cultivation, including their capacity to sequester CO\({}_{2}\) and produce value-added compounds [116; 117]. However, none of them provides a comprehensive and quantitative view of the order of magnitude of surface area, volume, biomass production, and the technological challenges that need to be overcome for this climate change mitigation strategy to become a reality. In this work, a wide review of the state-of-the-art microalgae culture is conducted, and the results indicate that it is technologically and logistically feasible to combat excess atmospheric CO\({}_{2}\) through biological sequestration. A production model for developing this capture system has also been proposed. However, this model must be reviewed, adapted, and adjusted for each location where its implementation would be planned. The computations indicate that the annual biological synthesis of 13 Gt of biomass could break CO\({}_{2}\) accumulation in the atmosphere. It assumes an average productivity of 17 g/m\({}^{2}\)-day for phytoplankton and a growth area of 2.1 \(\times\) 10\({}^{6}\) km\({}^{2}\) with a water column of 0.5 m in height. This depth would enhance the natural thermal control of the water mass by reducing the thermal inertia. With these dimensions, a volume of approximately 1000 km\({}^{3}\) would be required to synthesise this amount of biomass. This area could be divided into different production regions worldwide, which should be levelled and terraformed to be wholly isolated from the ground, with a depth of 1 to 2 m, and flooded in a controlled manner with seawater. Indeed, this would represent a further step in the current scale of phytoplankton production, where some companies already manage cultivation areas larger than 44 hectares [118]. In these systems, biomass production rates per unit area have been achieved that are quite similar, or even higher, to the used in the development of the present study (17 g/m2-day), indicating a good consistency in the proposed approach. Among them, the 35 g/m2-day proposed in [118], the 20.24 g/m2-day for a cultivation area of 605 m2 proposed in [119], and the 20 g/m2-day suggested in [120] are reliable examples. From here, the main technical and energy feasibility challenges are enumerated. First, it is necessary to select regions and latitudes with a proper climate to ensure the viability of the selected species, with low energy cost access to water and compatibility with human activities and natural ecosystems. Also, it is mandatory to optimise and reassess the pumping and aeration technologies because they are the only active mechanisms to promote growth. Finally, it is necessary to develop a technology for processing and/or locking the captured carbon in to regulate its flow and enable the recovery and recycling of macronutrients so as not to interfere with other human activities. The proposed global project cannot be carried out without commitment from and close collaboration among significant world powers. To encourage the project's success, these nations should establish a clear political framework and implement measures to drive its implementation forward. These policies should promote and facilitate the creation of socioeconomic infrastructure around this new industry, which can generate wealth and ensure its sustainability at the state or private level. For instance:  
1. A specialised scientific-technical sector should be implemented to design and propose suitable regions for establishing these CO2 sinks would be necessary. This sector should standardise the protocol for defining a region as suitable within a specific legal framework;
2. Measures that establish a profitable sector from the culture and harvest of phytoplankton and lead to the production of an attractive and valuable product for the market should be promoted;
3.