Photosynthetic living building material: Effect of the initial population of cyanobacteria on fixation of CO₂ and mechanical properties

Living building materials are regarded as environmentally friendly due to their minimal greenhouse gas emissions during the manufacturing process. In this study, a living building material (LBM) composed of sand, gelatin, and cyanobacteria was molded into 20 mm cubes with varying initial inoculation of cyanobacteria (1, 10, 100 units of biomass based on chlorophyll content). The atmospheric CO₂ fixation capacity, compressive strength, gelatin desiccation, microbial viability, and CaCO₃ content of the LBM cubes were measured during a 28-day curing period in the light chamber. The results indicated a positive correlation between the initial number of microbes, the rate of CO₂ fixation, and the rate of microbial growth. The compressive strength of the cubes was primarily influenced by gelatin desiccation until day 7, and by microbial mineral precipitation, which fortified the gelatin scaffold after day 7.