Mechanical and Civil Engineering Seminar

While the ancient alchemists strove to change lead into gold, modern day bio-geo-alchemists strive to turn sand into sandstone. The bio-geo-alchemy technology that has gained the most attention over the past 15 years is bio-mediated calcium carbonate precipitation via hydrolysis of urea (ureolysis), wherein microbes are used to induce precipitation of calcium carbonate (preferably calcite) in granular soils, turning cohesionless sand into a sandstone-like material. More recent research has looked at using another microbially-mediated processes, dissimilatory reduction of nitrogen, or denitrification, and at ureolysis using agriculturally-derived urease enzyme (as opposed to microbial urease) to precipitate calcium carbonate in soil. Denitrification offers the added benefit of desaturation via biogas generation. Successes in laboratory testing and limited field trials suggest that these techniques can non-disruptively mitigate the potential for earthquake-induced liquefaction under and around existing facilities. Induced carbonate precipitation may also be used to control fugitive dust and replace Portland cement as a binder in a variety of infrastructure construction applications. Induced carbonate precipitation is just one of many technologies currently being explored in the emerging field of biogeotechnical engineering.