Improved Biomass Production via Enhanced Inorganic Carbon Availability Using Crystalline Calcium Silicate Hydrate in a Marine Oleaginous Diatom Cultivation for Sustainable Aviation Fuel Production

Microalgae are promising feedstocks for sustainable aviation fuel (SAF) because of their high oil productivity and nonedible nature. In particular, Fistulifera solaris (F. solaris) is an oleaginous marine diatom that has attracted considerable attention as a potential feedstock for SAF production. However, low CO2 solubility limits biomass production. In addition, conventional carbonate-enrichment methods are often species-specific and carbon-intensive. In this study, cultivation using crystalline calcium silicate hydrate (cCSH), a low-cost and environmentally friendly material derived from concrete scrap and waste, was experimentally investigated to improve CO2 enrichment and biomass production. The addition of cCSH increased the dissolved inorganic carbon (DIC) concentration in the medium, mainly through the accumulation of bicarbonate ions (HCO3–). In the presence of cCSH, the DIC concentration was approximately 1.5-fold higher, and the biomass production of F. solaris increased 1.4-fold. The impact on greenhouse gas (GHG) emissions was calculated for a life-cycle microalgae-based SAF production process to evaluate the environmental impact of cCSH. With the introduction of cCSH, GHG emissions were estimated at 67.1 g-CO2eq/MJ, corresponding to an approximately 24.6% reduction compared with the conventional jet fuel. These results indicate that cCSH is a promising carbonate-enrichment material that enhances inorganic carbon supply and biomass production for SAF feedstock production.