Non‐ureolytic microbially induced carbonate precipitation: Investigating a cleaner biogeotechnical engineering pathway for soil mechanical improvement

Abstract

As the world's population grows, there is an increasing need for soil improvement techniques to accommodate construction demands. Current methods, most often, suffer from a high CO2 footprint, leading researchers to resort to biological methods of soil improvement through microbially induced carbonate precipitation (MICP). Commonly used ureolytic microbial carbonate precipitation produces ammonium ions, which can be environmentally concerning. The present study, therefore, addresses the use of non‐ureolytic MICP for soil improvement. The process of non‐ureolytic MICP relies on the use of heterotrophic bacteria to catalyze the oxidation reaction of organic compounds, eventually calcium carbonate precipitation. In this study, heterotrophic bacteria, such as Bacillus subtilis and Bacillus amyloliquefaciens, have been investigated as a solution for soil improvement via an ammonium‐free MICP. Calcium formate and calcium acetate are used as both calcium and carbon sources. This study, furthermore, examines the impact of MICP treatment on sandy soil and the effect of compaction level on treated samples. The findings indicate that the non‐ureolytic MICP method is an effective approach for stabilizing sand. The Calcium Formate‐B.Subtilis composition is shown to be the most effective compound for improving the unconfined compressive strength of sandy soils, while the Calcium Acetate‐B.Amyloliquefaciens composition is the least effective.