Biomining uses natural biological processes to extract minerals and metals from source ores, without the harmful environmental effects of conventional methods. It consists of two techniques: bioleaching and biooxidation, mainly used to extract copper and gold. Bioleaching involves using a weak sulfuric acid wash to promote bacterial growth, while biooxidation breaks down insoluble components of pyrite and arsenic. Biomining is a promising alternative to traditional refining methods, with 25% of current copper production using this method.
Biomining is a method of extracting minerals and metals from source ores using natural biological processes. The practice requires none of the environmentally harmful processes found in conventional refinement methods and instead relies entirely on the natural interaction of biological organisms. The process has also proven effective in profitably extracting minerals from low-grade and tailings ore previously considered unusable. Biomining consists of two different refinement techniques: bioleaching or biooxidation. Although the biological refining of minerals shows great promise in processing a number of elements, most biomining activity currently centers around the extraction of copper and gold.
Conventional methods of mining minerals rely on the application of toxic chemicals in the presence of extremely high temperatures; such processes often leave behind a legacy of environmental destruction, disease, and death. These factors have prompted the pursuit of cleaner and safer refining methods, more in line with the growing global push towards green solutions. Biomining has become one of the most promising of these which involves nothing but totally natural biological processes for its effectiveness. These refinement methods require little effort to set up, produce no toxic by-products or emissions, and require no external fuel sources. Represented by leaching and microbial oxidation processes, biological mineral mining has many potential application areas but is, currently, mainly used to process gold and copper.
The bioleaching process, one of the two refinement techniques, is a classic example of the simplicity of bioextraction methods. The low-grade ore is dumped into a pile known as a leach pile and soaked in a weak sulfuric acid wash. The acidic reaction with the sulfur matrix of the mineral promotes the growth of the Thiobaccilus ferrooxidans bacterial strain which degrades the mineral and releases the metallic or mineral deposits into a fluid solution. This mineral-rich liquid is collected and separated, and the residual sulfuric acid is reused for the next leach cycle.
The second biomining method, biooxidation, is widely used to prepare gold containing refractory ore for mining. This process involves exposing the mineral to bacterial oxidation which breaks down the otherwise insoluble components of pyrite and arsenic. This allows the mineral to be processed using much less aggressive methods with reduced environmental implications. This type of benefit has seen biomining rapidly grow as a viable alternative to traditional ore refining with 25% of the world’s current copper production being biomined. This trend is sure to continue as global pressure mounts for consumers and suppliers to become more environmentally responsible.
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