• Bioleaching;
  • Biohydrometallurgy;
  • Heavy metal;
  • Fly ash;
  • Waste incineration residue;
  • Renewable resource


A variety of both lithotrophic and organotrophic microorganisms are known to mediate the mobilization of various elements from solids mostly by the formation of inorganic and organic acids. Under appropriate environmental conditions, metals are solubilized and extracted from metal-rich materials in subsurface ecosystems by the action of bacteria and fungi. In mine tailings or landfills microbial metal leaching represents a potential environmental hazard. However, these microbial activities can be successfully applied in the industry for the recovery of metals from solid materials such as ores or incineration residues. Microbial leaching processes are currently used for the winning of gold and copper from low-grade ores (‘bioleaching’). Solid industrial waste materials such as fly ash, sludges, or dust might also be microbially treated to recover metals for the re-use in metal-manufacturing industries. Bioleaching allows the cycling of metals by a process close to natural biogeochemical cycles reducing the demand for resources such as ores, energy, or landfill space.