Microbial Caco3 Precipitation: for the Production of Biocement

The hydrolysis of urea by the widely distributed enzyme urease is special in that it is one of the few biologically occurring reactions that can generate carbonate ions without an associated production of protons. When this hydrolysis occurs in a calcium-rich environment, calcite (calcium carbonate) precipitates from solution forming a solid-crystalline material. The binding strength of the precipitated crystals is highly dependent on the rate of carbonate formation and under suitable conditions it is possible to control the reaction to generate hard binding calcite cement (or Biocement). The objective of this thesis was to develop an industrially suitable cost-effective microbial process for the production of urease active cells and investigate the potential for urease active cells to act as a catalyst for the production of Biocement. Several trials were conducted with unconsolidated sand and significant improvements in both shear strength (up to 1.8 MPa) and stiffness (up to 250 MPa) were achieved with a few days of treatment. Potential applications for the process are discussed.