Biomining
[2] The largest application currently being used is the treatment of mining waste containing iron, copper, zinc, and gold allowing for salvation of any discarded minerals.
[10] Following this experiment, the potential to use fungi to leach metals from their environment[11] and use microorganisms to take up radioactive elements like uranium and thorium[12] have also been explored.
[13] In western Europe the practice of extracting copper from metallic iron by placing it into drainage streams, used to be considered an act of alchemy.
[13] Cu2+ + Fe0 → Cu0 + Fe2+ In the Middle Ages in Portugal, Spain and Wales, miners unknowingly used this reaction to their advantage when they discovered that when flooding deep mine shafts for a period with some leftover iron they were able to obtain copper.
[15] Though the mechanism of oxidation via bacteria was not understood, the unintended use of biomining allowed copper production in China to reach 1000 Tons per year.
[15] Biological pre-treatment utilizes the natural oxidation abilities of microorganisms to remove unwanted minerals that interfere with the extraction of the target metals.
[16] While stirred tanks have been used to bioleach cobalt for copper mine tailings,[18] these are costly systems that can reach sizes of >1300m3 meaning that they are almost exclusively used for very high value minerals like gold.
In dump bioleaching, waste rock is piled into mounds (>100m tall) and saturated with sulfuric acid to encourage mineral oxidation from native bacteria.
[16] This finer grain is then stacked only 2 – 10 m high and is well irrigated allowing for plenty of oxygen and carbon dioxide to reach the bacteria.
[20] In situ Biomining, is the one current method utilizing bioleaching that serves as an effective and viable replacement for traditional mining.
[21] Because in-situ biomining, negates the need for the extraction of the ore bodies, this method stops the need for any hauling or smelting of the ore.[20] This would mean there would be no waste rocks or mineral tailings that contaminate the surface.
[24] There is great economic feasibility for in-situ biomining to replace traditional mining in a cheaper and more environmentally friendly way, however it has yet to be adopted on any large scale.
Electrons are pulled off of sulfur metal through oxidation and then put onto iron, producing reducing equivalents in the cell in the process.
Most industrial plants for biooxidation of gold-bearing concentrates have been operated at 40 °C with mixed cultures of mesophilic bacteria of the genera Acidithiobacillus or Leptospirillum ferrooxidans.
[28] Using Bacteria such as Acidithiobacillus ferrooxidans to leach copper from mine tailings has improved recovery rates and reduced operating costs.
Bioremediation is the process of using microbial systems to restore the environment to a healthy state by detoxifying and degrading environmental contaminants.
[30] Common mine and metal wastes include arsenic, cadmium, chromium, copper, lead, mercury, nickel and zinc which can make its way into the environment through rain and waterways where it can be moved long distances.
[5] After the applications, microbial assemblages were determined to be made up of 40% oil degrading bacteria, and one year later that number had fallen back to its baseline of around 1%.
[5] This case indicated that microbial bioremediation may work as a modern technique for restoring natural systems by removing toxins from the environment.
[6] BLSS do not usually contain biological component, however, the use of microorganisms to breakdown waste and regolith, while being able to capture their byproducts like nitrates and methane would theoretically allow for a cyclical system of regenerative life support.
[7] Like bacteria, fungi have been studied for their ability to extract rare earth elements and to process low grade ore.
[8] There has already been successful development of these hybrid biomaterials for eluting gold and molybdenite from solution, and this technique shows great promise for cleaning up tailing ponds.
