Biomining: News, Analysis and Sector Coverage

Biomining refers to the use of microorganisms, primarily bacteria and archaea, to extract metals from ores, concentrates, and waste materials. The most common technique is bioleaching, where bacteria oxidise sulphide minerals and release soluble metal ions that are then recovered by hydrometallurgical methods. Biomining is used commercially in copper and gold production and is under active development for cobalt, nickel, rare earth, and lithium recovery. It offers advantages over conventional smelting in terms of energy use and the ability to process low-grade or complex ores economically.

Biomining is the broader term for all applications of microorganisms in mineral extraction and processing. Bioleaching is the most common and commercially established biomining technique, referring specifically to the microbial oxidation of sulphide minerals to release dissolved metals. Biooxidation is a related process where bacteria are used not to directly dissolve the target metal but to oxidise the surrounding sulphide matrix, freeing refractory gold for subsequent cyanide leaching. Biomining also encompasses bioaccumulation and biosorption, where organisms concentrate metals from dilute solutions, though these are less commercially mature.

The most commercially important biomining bacteria are Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, both of which thrive in acidic, metal-rich environments and oxidise iron and sulphur compounds. Leptospirillum ferrooxidans is also widely present in bioleaching heaps and tanks. At higher temperatures, thermophilic archaea including Sulfolobus metallicus and Acidianus brierleyi are used in high-temperature bioleaching of copper and cobalt concentrates. Research programmes are actively developing and optimising microbial consortia for specific ore types and target metals, including rare earths and lithium.

Biomining operations carry several technical and environmental risks. Bioleaching heaps and tanks can produce acidic, metal-laden leachate that requires careful containment and treatment. The biological activity that drives the process can be disrupted by temperature extremes, pH fluctuations, or contamination with biocidal substances. Uncontrolled microbial activity in tailings and waste rock dumps, known as acid mine drainage, is a related phenomenon that causes ongoing environmental harm at many historic mining sites. At the commercial level, biomining is generally slower than conventional processing, which can affect capital efficiency and operational flexibility.

The most commercially significant examples of biomining are heap bioleaching operations for low-grade copper ores. The Cerro Verde mine in Peru and numerous Chilean copper operations use bacterial heap leaching to process oxide and secondary sulphide ores that are uneconomic to smelt. In gold production, biooxidation is used at the Barrick Goldstrike operation in Nevada and others to pre-treat refractory ores before cyanide leaching. The BIOX process, developed by Gold Fields and now widely licensed, is a tank bioleaching technology used at operations across Africa, Asia, and South America.