Insect frass as a substrate to stimulate native ureolytic bacteria for microbial-induced carbonate precipitation in soil biocementation

This study explored the use of freshly obtained insect waste (Frass-1) and composting insect waste (Frass-2) to stimulate highly active ureolytic bacterial cells for microbial-induced carbonate precipitation (MICP). The enriched bacterial cultures were utilized for soil biocementation treatment, and multiple analytical techniques were employed to investigate the biocemented soil. The optimal temperature for biomass production and urease activity was 30 °C at pH 8 for both samples. Surface strength and CaCO3 content analysis indicated that Frass-1 had slightly higher strength and CaCO3 content than Frass-2. Biomineral structures, such as hexagonal and spherical-shaped amorphous crystal formations, were observed in the biocemented soil samples. The Fourier transform infrared spectroscopic data of biocemented Frass-1 and Frass-2 soil samples revealed the presence of various functional groups and chemical components. X-ray diffraction analysis identified calcium magnesium carbonate and calcite as the main characteristic phases in Frass-1 and Frass-2, respectively. Thermal analysis of the MICP-treated soil samples revealed indicative changes in their mineralogical compositions. Finally, the durability of MICP-treated soil was evaluated under wet-dry and freeze–thaw cycles, showing an increase in mass loss with subsequent cycles. Ultimately, this study provides valuable insights into the potential of using frass for MICP in soil biocementation and its application in environmental engineering.