Fig. 5: Regeneration of NaOH via metathesis reaction using Ca(OH)2 derived from minerals and alkaline industrial wastes.

The ATT reaction produces high-purity H2 while fixing the seaweed carbon into solid carbonates (Na2CO3). The dry solid residue containing Na2CO3 can be regenerated on-site or easily transported to a centralized location for hydroxide regeneration. Ca(OH)2 from silicate minerals and alkaline industry wastes such as steel slag can be used to regenerate NaOH via a metathesis reaction. The regenerated NaOH is used for the subsequent ATT reaction cycle and the produced CaCO3 can be used as an industry product or stored to achieve the overall carbon negativity of the seaweed conversion technology.