Biocement stabilization of an experimental-scale artificial slope and the reformation of iron-rich crusts

Significance

Successful mine remediation is often the missing link in the circular and sustainable model for metal mining. Here, we provide compelling evidence that promoting the biogeochemical cycling of iron can be used to stabilize and remediate mine surfaces using crushed mine waste products. These microbially stabilized iron-rich crusts provide a surface similar to premining conditions that can be used to revegetate iron mine waste using the naturally rare plant species associated with these environments. Reformation of these iron-rich crusts will help to restore hydraulic function to degraded land sites and may provide an approach to reduce on the onset of acid mine drainage in sulphide-rich wastes.

Abstract

Novel biotechnologies are required to remediate iron ore mines and address the increasing number of tailings (mine waste) dam collapses worldwide. In this study, we aimed to accelerate iron reduction and oxidation to stabilize an artificial slope. An open-air bioreactor was inoculated with a mixed consortium of microorganisms capable of reducing iron. Fluid from the bioreactor was allowed to overflow onto the artificial slope. Carbon sources from the bioreactor fluid promoted the growth of a surface biofilm within the artificial slope, which naturally aggregated the crushed grains. The biofilms provided an organic framework for the nucleation of iron oxide minerals. Iron-rich biocements stabilized the artificial slope and were significantly more resistant to physical deformation compared with the control experiment. These biotechnologies highlight the potential to develop strategies for mine remediation and waste stabilization by accelerating the biogeochemical cycling of iron.