Copper mine tailings valorization using microbial induced calcium carbonate precipitation

Area of Science:

• Geotechnical Engineering
• Environmental Science
• Microbiology

Background:

• Copper mine tailings represent a significant waste stream requiring valorization.
• Microbial induced calcium carbonate precipitation (MICP) is a biological process with potential for material solidification.
• The ureolytic bacteria *Sporosarcina pasteurii* drives the MICP process.

Purpose of the Study:

• To investigate the solidification of copper mine tailings using MICP.
• To assess the toxicity of copper on *Sporosarcina pasteurii* during the MICP process.
• To evaluate the potential of MICP for valorizing copper mine tailings.

Main Methods:

• Bio-columns were grown using a submergent method with copper mine tailings.
• The compressive strength of bio-columns was measured.
• The depth of MICP reaction and crust formation were analyzed.

Main Results:

• Bio-columns from copper mine tailings exhibited a compressive strength of 0.54 MPa, lower than beach sand controls (1.85 MPa).
• Low porosity of tailings limited MICP reaction depth, forming a 1.8 mm crust.
• Particle size (<100 μm) was identified as a critical factor limiting the production of thick bio-cemented materials.

Conclusions:

• MICP is not suitable for producing thick bio-cemented materials from fine particles like copper mine tailings.
• The MICP process shows potential for creating thinner materials, such as bio-tiles.
• MICP could be used to cement toxic dust particles on mine tailings heaps.