Review of the use of microorganisms in geotechnical engineering applications

Until recently, engineers either ignored or neglected the role of microorganisms in geotechnical engineering. The microbially induced calcite precipitation (MICP) research technique is an innovative and relatively green technology which consists in a biological process through which microorganisms react with minerals (calcium source and cementation reagent) to produce calcite (CaCO3) as a byproduct that modifies and improves the engineering properties of soil. Laboratory and field results obtained from various studies are promising and viable, suggesting potential for various engineering applications. This research technique has also been considered to be useful in many engineering applications such as improvement of construction materials, cementation of porous media, improvement in strength and stiffness of engineering soils, hydraulic control of engineering facilities (waste containment), liquefaction, and erosion mitigation. In this review, the various methods of production of calcium carbonates (calcite), the role played by bacteria, various state-of-the-art procedures that have evolved in this research area, as well as ongoing studies are reported. Furthermore, the use of the MICP technique in remediation of contaminants and other environmental concerns is also presented. The advantages and challenges (in form of undesired byproducts) of this research technique are highlighted herein.