Sustainable biocementation of mine tailings: Reduction of urea requirements through bicarbonate-based MICP

Abstract

Microbially induced calcite precipitation (MICP) has emerged as a promising technique to contribute to a more sustainable management of mine tailings deposits. While ureolytic activity has been the predominant driver of conventional MICP to date, the associated release of ammonia poses significant environmental hazards. This study explores a novel, environmentally friendly approach by replacing urea with sodium bicarbonate as the carbon source for MICP, with the aim of reducing urea requirements and thus ammonia release. Leveraging the principles of the MICP, it was observed that when urea concentration was reduced to 0.7 M, by replacing it with bicarbonate, surface strength was close to 400 kPa. Furthermore, wind tunnel testing showed a significant reduction in dust emission, where the mass loss rate of the biocemented sample was below 10 kg m⁻² h⁻¹, which means a 9-fold reduction compared to untreated samples. So, it was demonstrated that bicarbonate can effectively replace urea, achieving a relevant reduction of up to 75 % in urea use without compromising the surface strength of the biocemented tailings and reducing the environmental hazards of ammonia release. These results highlight the potential of bicarbonate-based MICP as an innovative and sustainable approach to mitigate the environmental impacts associated with tailings deposits.