Cyanobacteria are photosynthetic microorganisms found in a variety of environments, including marine water bodies. Some species are able to perform biomineralization, producing minerals such as calcium carbonate (CaCO3) that may act as biocement. The biomineralization capability of cyanobacteria has already been explored in the development of Living Building Materials (LBMs), composed of an inert scaffold of sand and hydrogel, that contributes to CO2 capture.

The offshore industry is a significant user of concrete, contributing to 11% of the global CO2 emissions. Therefore, the application of cyanobacteria biomineralized materials is envisioned as a way to reduce CO2 emissions in this sector.

The cyanobacteria biomineralized material has been studied in the fields of construction and is applied in 3D printing, but its potential for offshore applications still needs to be explored.

This study aims to explores the proprieties of cyanobacteria biomineralized materials to catter some requirements of offshore applications, thereby contributing to a more sustainable practice. This was done by first recreating the material from other studies, assessing its mechanical proprieties and testing it in underwater conditions. This was followed by a tinkering process where material qualities (e.g., cyanobacteria optical density (OD), biomineralization/curing time, type of hydrogel, aditional coating) were adjusted to fullfill its purposes.

The impact of these changes were measured through submerging the material in seawater and assessing its mechanical proprieties.

The use of cyanobacteria at an OD of 2.4, resulted in the strongest material. Using agar as an hydrogel binder, countered the dissolvability of the material with a gelatine binder. On the other hand mechanical tests showed that the agar bonded material was significantly weaker than the gelatine bonded material. Adding a silicone rubber coating to the gelatine bonded material did not make the material resistant to seawater. A prolonged biomineralization time improved the strength of the material significantly but more exploration is required to determine if the biomineralization time is the result of this strength or the adjusted sand/medium ratio.

Overall, this study demonstrated that cyanobacteria biomineralized materials can be applied in offshore applications since the right cyanobacteria OD, binder, coating and biomineralization time are employed.