Foam-based microbially-induced calcite precipitation

Abstract

Building on the development history of the Microbially Induced Calcite Precipitation (MICP) method and recent insights into the organization of liquid and bubbles within pore spaces filled with liquid foam, we hypothesize a potential synergy between MICP and liquid foam for enhancing soil properties. We assess the respiration and calcification capabilities of the bacterium Sporosarcina pasteurii in various foaming solutions formulated with bio-based surfactants. The most promising formulations are then used for in-situ observations of bacteria-induced calcification within foam-embedded 2D granular packings. We observe that maltoside-type AlkylPolyGlucosides with relatively short chains, in particular, enable optimal calcification in less than an hour. In the granular packing, the foam spontaneously creates liquid zones enriched with bacteria at the inter-grain contacts. As a result, instead of being distributed across the entire porous space, calcification is localized in these zones, promoting the formation of solid bridges (CaCO${}_3$). This suggests that the foam-based MICP method could represent a relevant variation of the original approach, though this remains to be confirmed at larger scales through mechanical testing on representative soil samples.