Biomining

{{expert|Biology|date=March 2026}} {{short description|Technique of extracting metals from ores using prokaryotes or fungi}} {{distinguish|Bioprospecting}} '''Biomining''' refers to processes that use organisms to extract metals from ores and other solid materials.<ref name=":03">{{Cite journal |last=Jerez |first=Carlos A |date=2017 |title=Biomining of metals: how to access and exploit natural resource sustainably. |journal=Microbial Biotechnology |volume=10 |issue=5 |pages=1191–1194 |doi=10.1111/1751-7915.12792 |pmid=28771998 |pmc=5609284 |issn=1751-7915}}</ref> The largest application currently being used is the treatment of mining waste containing iron, copper, zinc, and gold. It may also be useful in maximizing the yields of increasingly low grade ore deposits.<ref name="kundu20142">Kundu et al. 2014 [http://www.hindawi.com/journals/jmin/2014/290275/ "Biochemical Engineering Parameters for Hydrometallurgical Processes: Steps towards a Deeper Understanding"]</ref> Biomining has been proposed as a relatively environmentally friendly alternative and/or supplementation to traditional mining.<ref name=":03"/> Current methods of biomining are modified leach mining processes.<ref name=":3">{{Cite journal |last=Johnson |first=D Barrie |date=2014 |title=Biomining—biotechnologies for extracting and recovering metals from ores and waste materials |url=https://linkinghub.elsevier.com/retrieve/pii/S0958166914000809 |journal=Current Opinion in Biotechnology |language=en |volume=30 |pages=24–31 |doi=10.1016/j.copbio.2014.04.008|pmid=24794631 |url-access=subscription }}</ref> These aptly named bioleaching processes most commonly includes the inoculation of extracted rock with bacteria and acidic solution, with the leachate salvaged and processed for the metals of value.<ref name=":3" /> Aspirational applications include space biomining, fungal bioleaching and biomining with hybrid biomaterials.<ref name=":82">{{Cite journal |last1=Santomartino |first1=Rosa |last2=Zea |first2=Luis |last3=Cockell |first3=Charles S. |date=2022-01-06 |title=The smallest space miners: principles of space biomining |journal=Extremophiles |language=en |volume=26 |issue=1 |page=7 |doi=10.1007/s00792-021-01253-w |issn=1433-4909 |pmc=8739323 |pmid=34993644}}</ref><ref name=":92">{{Cite journal |last1=Dusengemungu |first1=Leonce |last2=Kasali |first2=George |last3=Gwanama |first3=Cousins |last4=Mubemba |first4=Benjamin |date=October 2021 |title=Overview of fungal bioleaching of metals |url=https://linkinghub.elsevier.com/retrieve/pii/S2666765721000545 |journal=Environmental Advances |language=en |volume=5 |article-number=100083 |doi=10.1016/j.envadv.2021.100083|bibcode=2021EnvAd...500083D |doi-access=free }}</ref>

Biomining is related to '''biohydrometallurgy''', a subset or specialized form of hydrometallurgy, which refers to the use of aqueous solutions for metal extraction through a series of chemical reactions. In biohydrometallurgy, the aqueous solutions contain biological agents (bacteria), which assist in the recovery of metals.<ref>{{cite book |last1=Free |first1=Michael |title=Hydrometallurgy : Fundamentals and Applications |date=October 7, 2013 |publisher=John Wiley & Sons, Incorporated |isbn=9781118230770 |pages=13–14 |url=https://public.ebookcentral.proquest.com/choice/publicfullrecord.aspx?p=1338474 |access-date=April 25, 2021}}</ref><ref>Rossi, G. (1990). Biohydrometallurgy, Hamburg: McGraw-Hill. {{ISBN|3-89028-781-6}}</ref> '''Bioleaching''' is closely related to biohydrometallurgy. It focuses on extraction or liberation of metals from their ores through the use of living organisms.<ref name= Bosecker/> Relative to traditional forms of metallurgy, biohydrometallurgy or bioleaching is slow but in principle low cost.<ref name=elec>{{Cite journal |title=Application of bioleaching to copper mining in Chile |journal=Electronic Journal of Biotechnology |last=Gentina |first=Juan Carlos |url=https://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582013000300016 |volume=16 |issue=3 |last2=Acevedo |first2=Fernando |doi=10.2225/vol16-issue3-fulltext-12}}</ref> These techniques are mainly applied to recovery of copper and gold from low-grade ores. These techniques have been proposed to the extraction of uranium, nickel, and other metals.<ref name=Gale>{{Cite web|url=https://link.gale.com/apps/doc/GALE%7CCV2644150164/OVIC|title=Biohydrometallurgy|last=Blanchfield|first=Deirdre|date=January 21, 2018|website=galeapps.gale.com|series=Environmental Encyclopedia|url-access=subscription|archive-url=|archive-date=|access-date=2020-04-12}}</ref>

==History== The possibility of using microorganisms in biomining applications was realized after the 1951 paper by Kenneth Temple and Arthur Colmer.<ref name=":14">{{Cite journal |last1=Temple |first1=Kenneth L. |last2=Colmer |first2=Arthur R. |date=1951 |title=THE AUTOTROPHIC OXIDATION OF IRON BY A NEW BACTERIUM: THIOBACILLUS FERROOXIDANS1 |journal=Journal of Bacteriology |volume=62 |issue=5 |pages=605–611 |doi=10.1128/jb.62.5.605-611.1951 |issn=0021-9193 |pmid=14897836|pmc=386175 }}</ref> In the paper the authors presented evidence that the bacteria ''Acidithiobacillus ferrooxidans'' (basonym ''Thiobacillus ferrooxidans'') is an iron oxidizer that thrive in iron, copper and magnesium-rich environments.<ref name=":14"/> In the experiment, ''A. ferrooxidans'' was inoculated into media containing between 2,000 and 26,000 ppm ferrous iron, finding that the bacteria grew faster and were more motile in the high iron concentrations.<ref name=":14"/> The byproducts of the bacterial growth caused the media to turn very acidic, in which the microorganisms still thrived.<ref>{{cite journal|last1=Johnson|first1=D Barrie|title=Biomining—biotechnologies for extracting and recovering metals from ores and waste materials|journal=Current Opinion in Biotechnology|date=December 2014|volume=30|pages=24–31|doi=10.1016/j.copbio.2014.04.008|pmid=24794631}}</ref> Following this experiment, the potential to use fungi to leach metals from their environment<ref name=":2">{{cite journal |last1=Wang |first1=Y. |last2=Zeng |first2=W. |last3=Qiu |first3=G. |last4=Chen |first4=X. |last5=Zhou |first5=H. |date=15 November 2013 |title=A Moderately Thermophilic Mixed Microbial Culture for Bioleaching of Chalcopyrite Concentrate at High Pulp Density |journal=Applied and Environmental Microbiology |volume=80 |issue=2 |pages=741–750 |doi=10.1128/AEM.02907-13 |pmc=3911102 |pmid=24242252}}</ref> and use microorganisms to take up radioactive elements like uranium and thorium<ref>{{Cite book |last=Tsezos |first=Marios |title=Geobiotechnology I |date=2013-01-01 |publisher=Springer Berlin Heidelberg |isbn=978-3-642-54709-6 |editor-last=Schippers |editor-first=Axel |series=Advances in Biochemical Engineering/Biotechnology |volume=141 |pages=173–209 |language=en |chapter=Biosorption: A Mechanistic Approach |doi=10.1007/10_2013_250 |pmid=24368579 |editor-last2=Glombitza |editor-first2=Franz |editor-last3=Sand |editor-first3=Wolfgang}}</ref> have also been explored.<ref name=":2" />

While the 1960s was when industrial biomining got its start, humans have been unknowingly using biomining practices for hundreds of years.<ref name=":4">{{Cite book |url=http://link.springer.com/10.1007/978-90-481-9204-5 |title=Geomicrobiology: Molecular and Environmental Perspective |date=2010 |publisher=Springer Netherlands |isbn=978-90-481-9203-8 |editor-last=Barton |editor-first=Larry L. |location=Dordrecht |language=en |doi=10.1007/978-90-481-9204-5 |editor-last2=Mandl |editor-first2=Martin |editor-last3=Loy |editor-first3=Alexander}}</ref> 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.<ref name=":4" /> However, today we know that it is a fairly simple chemical reaction.<ref name=":4" />

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.<ref name=":62">{{Cite journal |last=Johnson |first=D. Barrie |date=2015 |title=Biomining goes underground |url=https://www.nature.com/articles/ngeo2384 |journal=Nature Geoscience |language=en |volume=8 |issue=3 |pages=165–166 |doi=10.1038/ngeo2384 |bibcode=2015NatGe...8..165J |issn=1752-0894|url-access=subscription }}</ref>

In China, the use of biomining techniques has been documented as early as 6th-7th century BC.<ref name=":11">{{Citation |last1=Qiu |first1=Guanzhou |title=Biomining in China: History and Current Status |date=2023 |work=Biomining Technologies |pages=151–161 |editor-last=Johnson |editor-first=David Barrie |url=https://link.springer.com/10.1007/978-3-031-05382-5_8 |access-date=2024-03-28 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-031-05382-5_8 |isbn=978-3-031-05381-8 |last2=Liu |first2=Xueduan |last3=Zhang |first3=Ruiyong |editor2-last=Bryan |editor2-first=Christopher George |editor3-last=Schlömann |editor3-first=Michael |editor4-last=Roberto |editor4-first=Francisco Figueroa|url-access=subscription }}</ref> The relationship between water and ore to produce copper was well documented, and during the Tang dynasty and Song dynasty copper was produced using hydrometallurgical techniques.<ref name=":11" /> 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.<ref name=":11" />

Biomining was first used more than 300 years ago to recover copper.<ref name=elec>{{Cite journal |title=Application of bioleaching to copper mining in Chile |journal=Electronic Journal of Biotechnology |last=Gentina |first=Juan Carlos |url=https://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-34582013000300016 |volume=16 |issue=3 |last2=Acevedo |first2=Fernando |doi=10.2225/vol16-issue3-fulltext-12}}</ref><ref name=Gale>{{Cite web|url=https://link.gale.com/apps/doc/GALE%7CCV2644150164/OVIC|title=Biohydrometallurgy|last=Blanchfield|first=Deirdre|date=January 21, 2018|website=galeapps.gale.com|series=Environmental Encyclopedia|url-access=subscription|archive-url=|archive-date=|access-date=2020-04-12}}</ref><ref>{{cite book |last1=Komnitsas |first1=Kostas |title=Recent Advances in Hydro- and Biohydrometallurgy |date=July 2019 |publisher=Multidisciplinary Digital Publishing Institute |isbn=978-3-03921-299-6 |pages=ix |url=https://www.mdpi.com/books/pdfview/book/1460 |access-date=April 25, 2021}}</ref><ref>{{cite book |last1=Free |first1=Michael |title=Treatise on Process Metallurgy |date=2014 |publisher=Elsevier |isbn=9780080969879 |pages=983–993 |url=https://www.sciencedirect.com/science/article/pii/B9780080969886000201 |access-date=April 26, 2021}}</ref> Early work on copper bioleaching was carried out at the mines of Chuquicamata and Lo Aguirre in Chile.<ref>{{Cite book |title=Biomining|publisher=Springer |last=Domic |first=Esteban M. |year=2007 |isbn=978-3-540-34909-9 |url= |editor-last=Rawlings |editor-first=D.E |chapter=A Review of the Development and Current Status of Copper Bioleaching Operations in Chile: 25 Years of Successful Commercial Implementation |editor-last2=Johnson |editor-first2=B.D.}}</ref>

==Mechanism== thumb|347x347px|A Simplified scheme illustrating bioleaching of copper from its ore chalcopyrite The processes often involve the use ferric ions (Fe³⁺) for oxidation of sulfide minerals.<ref name="Johnson">{{Cite journal|last1=Johnson|first1=D. Barrie|last2=Kanao|first2=Tadayoshi|last3=Hedrich|first3=Sabrina|date=2012-01-01|title=Redox Transformations of Iron at Extremely Low pH: Fundamental and Applied Aspects|journal=Frontiers in Microbiology|language=English|volume=3|page=96|doi=10.3389/fmicb.2012.00096|issn=1664-302X|pmc=3305923|pmid=22438853|doi-access=free}}</ref> The organisms that promote these reactions tolerate high metal concentrations and low pH: :CuFeS₂+4H⁺+O₂ → Cu²⁺+Fe²⁺+2S⁰+2H₂O

:4Fe²⁺ + 4H⁺ + O₂ → 4Fe³⁺ + 2H₂O

:2S⁰ + 3O₂+2H₂O → 2 SO^2-₄ + 4H⁺,

:CuFeS₂ + 4Fe³⁺ → Cu²⁺ + 2 S⁰ + 5 Fe²⁺

==Bioleaching technologies== ===Direct vs indirect leaching=== Biohydrometallurgy can be productively implemented in two ways: direct and indirect leaching. Direct leaching entails physical contact between the ore and the microbe. The sulfide ore serves as an electron donor, which supplies energy to the organisms when coupled to the reduction of oxygen. Many sulfide ores are susceptible to direct leaching: covelite (CuS), chalcocite (Cu₂S), galena (PbS), molybdenite (MoS₂), and more. The energy producing conversion can be represented: :{{chem2|MS + 2 O2 -> MSO4}}

"Indirect leaching" requires no physical contact between the organism and the sulfide mineral. Here, the bacteria produce Fe³⁺ (ferric) ions, which can be viewed as the lixiviant. Ferric ions attack the sulfide (usually) ore. The general equation for the solubilization of a metal sulfide ore is: :{{chem2|MS + Fe2(SO4)3 + O2 -> 2 FeSO4 +MSO4 + S}} Here the target of the biomining is M, often copper. The bacteria can then promote the re-oxidation of ferrous by air and the oxidation of sulfur-containing products to sulfuric acid.

The oxidation of the pyrite is of particular interest in gold recovery for gold-containing pyrite (and related "pyritic" minerals). The goal here is to solubilize pyrite using air:<ref name=UllmannCu>{{cite book |last1=Lossin |first1=Adalbert |title=Ullmann's Encyclopedia of Industrial Chemistry |chapter=Copper |date=2001 |doi=10.1002/14356007.a07_471 |isbn=978-3-527-30385-4 }}</ref> :{{chem2|FeS2 + O2 + 2 H2O -> FeSO4 + 2 H2SO4}}

In terms of mechanism, an early step entails oxidation of pyrite to thiosulfate by ferric ion (Fe³⁺), which in turn is reduced to give ferrous ion (Fe²⁺). Thiosulfate is also oxidized by air to give sulfate: :{{chem2|S2O3(2-) + 2 O2 + H2O -> 2HSO4-}}

The oxidation of the ferrous ion by air is promoted by bacteria: :{{chem2|4 FeSO4 + O2 + 2 H2SO4 -> 2Fe2(SO4)3 + 2 H2O}}

Thus the roles of the bacteria are the oxidations of the ferrous and thiosulfate. As a practical matter, the bacteria require nutrients such as ammonium and phosphate.<ref name= Bosecker>{{cite journal |last1=Bosecker |first1=K. |title=Bioleaching: Metal solubilization by microorganisms |journal=FEMS Microbiology Reviews |date=1997 |volume=20 |issue=3–4 |pages=591–604 |doi=10.1016/S0168-6445(97)00036-3}}</ref><ref name=":32">{{Cite journal |last=Johnson |first=D Barrie |date=2014 |title=Biomining—biotechnologies for extracting and recovering metals from ores and waste materials |url=https://linkinghub.elsevier.com/retrieve/pii/S0958166914000809 |journal=Current Opinion in Biotechnology |language=en |volume=30 |pages=24–31 |doi=10.1016/j.copbio.2014.04.008|url-access=subscription }}</ref>

The sulfate salts are metal aquo complexes, not anhydrous as depicted.

Similar reactions apply to the proposed leaching of nickel ions from pentlandite ores and uranium from UO2-containing ores.<ref name=UllmannCu/>

===Heap or dump leaching=== Bioleaching was one of the first widely used applications of biomining.<ref>{{cite book |last1=Voeste |first1=Theodor |last2=Weber |first2=Klaus |last3=Hiskey |first3=Brent |last4=Brunner |first4=Gerd |title=Ullmann's Encyclopedia of Industrial Chemistry |chapter=Liquid–Solid Extraction |date=2006 |doi=10.1002/14356007.b03_07.pub2 |isbn=978-3-527-30385-4 }}</ref> It is practiced in two broad venues: *rock is treated with an extractant (lixiviant), which percolates through the solid and the metals are recovered from the leachate.<ref name=black>{{cite journal |last1=Anjum |first1=Fozia |last2=Shahid |first2=Muhammad |last3=Akcil |first3=Ata |title=Biohydrometallurgy techniques of low grade ores: A review on black shale |journal=Hydrometallurgy |date=2012 |volume=117-118 |pages=1–12 |doi=10.1016/j.hydromet.2012.01.007}}</ref> **Dump bioleaching, waste rock is piled into mounds (>100m tall) and saturated with sulfuric acid to encourage mineral oxidation from native bacteria.<ref name=":32" /> Inoculation of the rock with bacteria is often not performed in dump bioleaching which instead relies on the bacteria already present in the rock.<ref name=":32" /> **Heap bioleaching is a newer take on dump leaching.<ref name=":32" /> The process includes more processing in which the rocks are ground into a finer grain size.<ref name=":32" /> 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.<ref name=":32" /> The mounds are also often inoculated with bacteria.<ref name=":32" /> The liquid coming out at the bottom of the pile, called leachate, is rich in the processed mineral. The heaps reside on non-porous platforms which catch the leachate for processing.<ref name=":32" /> Once collected the leachate is transported to a precipitation plant where the metal is reprecipitated and purified. The waste liquid, now void of the valuable minerals, can be pumped back to the top of the pile and the cycle is repeated.<ref name=":32" /> The temperature inside the leach dump often rises spontaneously as a result of microbial activities.<ref name=":32" /> Thus, thermophilic iron-oxidizing chemolithotrophs such as thermophilic ''Acidithiobacillus'' species and ''Leptospirillum'' and at even higher temperatures the thermoacidophilic archaeon ''Sulfolobus (Metallosphaera sedula)'' may become important in the leaching process above 40&nbsp;°C.<ref name=":32" /> thumb|324x324px|In situ copper biomining of and electro-winning for recovery from Kupferschiefer deposits

===Stirred tank=== A major alternative to heap or dump leaching is continuously stirred tank reactor (STR).<ref name=black/> Alternatives include the airlift reactor (ALR) or pneumatic reactor (PR) of the Pachuca type to extract the low concentration mineral resources efficiently.<ref name="kundu20142"/>

=== ''In situ'' biomining === ''In situ'' biomining involves the flooding and inoculation of fractured ore bodies that have yet to be removed from the ground.<ref name=":32" /> Once the bacteria are introduced to the ore deposits, they begin leaching the precious metals, which can then be extracted as leachate with a recovery well.<ref>{{Cite journal |last=Zhang |first=Ruiyong |last2=Hedrich |first2=Sabrina |last3=Ostertag-Henning |first3=Christian |last4=Schippers |first4=Axel |date=June 2018 |title=Effect of elevated pressure on ferric iron reduction coupled to sulfur oxidation by biomining microorganisms |url=https://linkinghub.elsevier.com/retrieve/pii/S0304386X18301889 |journal=Hydrometallurgy |language=en |volume=178 |pages=215–223 |doi=10.1016/j.hydromet.2018.05.003|doi-access=free }}</ref> In-situ mining also shows promise for applications in cost-effective deep subsurface extraction of metals.<ref name=":63">{{Cite journal |last=Johnson |first=D. Barrie |date=2015 |title=Biomining goes underground |url=https://www.nature.com/articles/ngeo2384 |journal=Nature Geoscience |language=en |volume=8 |issue=3 |pages=165–166 |doi=10.1038/ngeo2384 |issn=1752-0894|url-access=subscription }}</ref>

''In situ'' biomining, is the one current method utilizing bioleaching that serves as an effective and viable replacement for traditional mining.<ref name=":133">{{Cite journal |last=Martínez‐Bellange |first=Patricio |last2=von Bernath |first2=Diego |last3=Navarro |first3=Claudio A. |last4=Jerez |first4=Carlos A. |date=January 2022 |title=Biomining of metals: new challenges for the next 15 years |url=https://sfamjournals.onlinelibrary.wiley.com/doi/10.1111/1751-7915.13985 |journal=Microbial Biotechnology |language=en |volume=15 |issue=1 |pages=186–188 |doi=10.1111/1751-7915.13985 |issn=1751-7915 |pmc=8719796 |pmid=34846776}}</ref> Because ''in-situ'' biomining, negates the need for the extraction of the ore bodies, this method stops the need for hauling or smelting of the ore.<ref name=":63" /> This would mean there would be no waste rocks or mineral tailings that contaminate the surface.<ref name=":63" /> In-situ biomining poses environmental challenges, such as the contamination of ground water.<ref name=":63" /><ref name=":133" />

== Applications == === Gold === Bioleaching from pyritic ores (pyrite, marcasite, arsenopyrite) utilize iron- and sulfur-oxidizing bacteria, including ''Acidithiobacillus ferrooxidans'' (formerly known as ''Thiobacillus ferrooxidans'') and ''Acidithiobacillus thiooxidans '' (formerly known as ''Thiobacillus thiooxidans''). There is no interest in obtaining iron salts from this kind of treatment. Rather, traces of precious metals such as gold may be liberated in the process since tiny particles of gold are often associated with pyrite.<ref>{{cite book |doi=10.1016/B978-0-12-804022-5.00014-1 |chapter=Experimental and Research Methods in Metals Biotechnology |title=Biotechnology of Metals |year=2018 |last1=Natarajan |first1=K.A. |pages=433–468 |isbn=978-0-12-804022-5 }}</ref> Sulfuric acid is produced in the processing of these pyritic ores,<ref>{{Cite book|last=Dr. R.C. Dubey|title=A textbook of biotechnology: for university and college students in India and abroad|year=1993|isbn=978-81-219-2608-9|location=New Delhi|page=442|oclc=974386114}}</ref> using indirect leaching. Plants for biooxidation of gold-bearing concentrates have been operated at 40&nbsp;°C with mixed cultures of ''Leptospirillum ferrooxidans'' or of the genera ''Acidithiobacillus''. Gold is frequently found in nature associated with arsenopyrite and pyrite. In the microbial leaching process ''Acidithiobacillus ferrooxidans'', etc. dissolve these minerals, exposing trapped gold (Au).<ref name=":5"/> The following reaction summarizes the process:<ref name=":5">{{Cite journal |last=Li |first=Qian |last2=Luo |first2=Jun |last3=Xu |first3=Rui |last4=Yang |first4=Yongbin |last5=Xu |first5=Bin |last6=Jiang |first6=Tao |last7=Yin |first7=Huaqun |date=2021 |title=Synergistic enhancement effect of Ag+ and organic ligands on the bioleaching of arsenic-bearing gold concentrate |url=https://linkinghub.elsevier.com/retrieve/pii/S0304386X21001729 |journal=Hydrometallurgy |language=en |volume=204 |article-number=105723 |doi=10.1016/j.hydromet.2021.105723 |doi-access=free}}</ref> :2 FeAsS[Au] + 7 O₂ + 2 H₂O + H₂SO₄ → Fe₂(SO₄)₃ + 2 H₃AsO₄ + [Au]

===Copper ores=== One of the largest applications of these leaching methods is in the mining of copper. ''Acidithiobacillus ferrooxidans'' has the ability to solubilize copper from its sulfidic ores.<ref>{{Cite journal |last1=Valdés |first1=Jorge |last2=Pedroso |first2=Inti |last3=Quatrini |first3=Raquel |last4=Dodson |first4=Robert J |last5=Tettelin |first5=Herve |last6=Blake |first6=Robert |last7=Eisen |first7=Jonathan A |last8=Holmes |first8=David S |date=2008 |title=Acidithiobacillus ferrooxidans metabolism: from genome sequence to industrial applications |journal=BMC Genomics |language=en |volume=9 |issue=1 |page=597 |doi=10.1186/1471-2164-9-597 |doi-access=free |issn=1471-2164 |pmc=2621215 |pmid=19077236}}</ref> The acidophilic archaea ''Sulfolobus metallicus'' and ''Metallosphaera sedula'' can tolerate up to 4% of copper. The main application is for extraction from low grade ores using ''Thiobacillus thiooxidans''.<ref name=UllmannCu/> – an important consideration in the face of the depletion of high grade ores.<ref name="kundu20142"/>

The copper can then be recovered from the solution by plating it out on scrap iron or electrowinning. :Fe⁰ + Cu²⁺ → Cu⁰ + Fe²⁺

The main copper mineral chalcopyrite (CuFeS₂) is not leached very efficiently. Instead, the dominant technology remains flotation. The leaching of CuFeS₂ proceeds according the route indicated for indirect leaching above.<ref name=UllmannCu/>

===Uranium=== Bioleaching of non-sulfidic ores such as pitchblende also uses ferric iron as an oxidant (e.g., UO₂ + 2 Fe³⁺ ==> UO₂²⁺ + 2 Fe²⁺). In this case, the purpose of the bacterial step is the regeneration of Fe³⁺. Sulfidic iron ores can be added to speed up the process and provide a source of iron. Bioleaching of non-sulfidic ores by layering of waste sulfides and elemental sulfur, colonized by ''Acidithiobacillus'' spp., has been demonstrated, which provides a strategy for accelerated leaching of materials that do not contain sulfide minerals.<ref>{{Cite journal|doi = 10.1021/es900986n|title = Bioleaching of Ultramafic Tailings by ''Acidithiobacillusspp''. For CO2Sequestration|year = 2010|last1 = Power|first1 = Ian M.|last2 = Dipple|first2 = Gregory M.|last3 = Southam|first3 = Gordon|journal = Environmental Science & Technology|volume = 44|issue = 1|pages = 456–462|pmid = 19950896|bibcode = 2010EnST...44..456P}}</ref>

Biomining was used in Canada in the 1970s to extract additional uranium out of exploited mines.<ref>{{Cite book |last=McCready |first=RGL |title=Microbial Mineral Recovery |last2=Gould |first2=WD |date=1990 |publisher=McGraw-Hill |pages=107–125 |chapter=Bioleaching of Uranium}}</ref> As in the biomining of copper, ''Acidithiobacillus ferrooxidans'' can oxidize U⁴⁺ to U⁶⁺ with O₂ as electron acceptor. However, it is likely that the uranium leaching process depends more on the chemical oxidation of uranium by Fe³⁺, with ''At. ferrooxidans'' contributing mainly through the reoxidation of Fe²⁺ to Fe³⁺. :UO₂ + Fe₂(SO₄)₃ → UO₂SO₄ + 2 FeSO₄

==Aspirational themes== Additional capabilities, of current bioleaching technologies include the bioleaching of metals from sulfide ores, phosphate ores, and concentrating of metals from solution.<ref name=":3" /> For example, the bioleaching of cobalt mine tailings has been investigated using stirred tanks.<ref>{{Citation |last=Morin |first=Dominique Henri Roger |title=Bioleaching of a Cobalt-Containing Pyrite in Stirred Reactors: a Case Study from Laboratory Scale to Industrial Application |date=2007 |work=Biomining |pages=35–55 |editor-last=Rawlings |editor-first=Douglas E. |url=http://link.springer.com/10.1007/978-3-540-34911-2_2 |access-date=2024-02-17 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |language=en |doi=10.1007/978-3-540-34911-2_2 |isbn=978-3-540-34909-9 |last2=d'Hugues |first2=Patrick |editor2-last=Johnson |editor2-first=D. Barrie|url-access=subscription }}</ref> thumb|323x323px|Illustration of the process of uranium heap leaching. In bioleaching, the heap would have been inoculated with the process specific microbe.

===Coal desulfurization=== Biological methods have shown some promise for the removal of sulfur from coal, giving a cleaner-burning fuel. This concept has not progressed beyond demonstration phase, however.<ref>{{Cite book |last1=Chiang |first1=Shiao-Hung |last2=Cobb |first2=James T. |title=Kirk-Othmer Encyclopedia of Chemical Technology |chapter=Coal Conversion Processes, Cleaning and Desulfurization |date=2000 |doi=10.1002/0471238961.0312050103080901.a01 |isbn=978-0-471-48494-3 }}</ref>

=== Biomining in space === thumb|276x276px|Theoretical map of space biomining/bioleaching based biological life support system (BLSS) Microorganisms could be employed to mine extraterrestrially.<ref>{{cite journal |last1=Cockell |first1=Charles S. |last2=Santomartino |first2=Rosa |last3=Finster |first3=Kai |last4=Waajen |first4=Annemiek C. |last5=Eades |first5=Lorna J. |last6=Moeller |first6=Ralf |last7=Rettberg |first7=Petra |last8=Fuchs |first8=Felix M. |last9=Van Houdt |first9=Rob |last10=Leys |first10=Natalie |last11=Coninx |first11=Ilse |last12=Hatton |first12=Jason |last13=Parmitano |first13=Luca |last14=Krause |first14=Jutta |last15=Koehler |first15=Andrea |last16=Caplin |first16=Nicol |last17=Zuijderduijn |first17=Lobke |last18=Mariani |first18=Alessandro |last19=Pellari |first19=Stefano S. |last20=Carubia |first20=Fabrizio |last21=Luciani |first21=Giacomo |last22=Balsamo |first22=Michele |last23=Zolesi |first23=Valfredo |last24=Nicholson |first24=Natasha |last25=Loudon |first25=Claire-Marie |last26=Doswald-Winkler |first26=Jeannine |last27=Herová |first27=Magdalena |last28=Rattenbacher |first28=Bernd |last29=Wadsworth |first29=Jennifer |last30=Craig Everroad |first30=R. |last31=Demets |first31=René |title=Space station biomining experiment demonstrates rare earth element extraction in microgravity and Mars gravity |journal=Nature Communications |date=10 November 2020 |volume=11 |issue=1 |page=5523 |doi=10.1038/s41467-020-19276-w |pmid=33173035 |pmc=7656455 |bibcode=2020NatCo..11.5523C |url=|language=en |issn=2041-1723}} 50px Available under [https://creativecommons.org/licenses/by/4.0/ CC BY 4.0].</ref>

Space biomining is at the conceptual stage.<ref name=":82"/><ref name="New Scientist">{{cite news |last1=Crane |first1=Leah |title=Asteroid-munching microbes could mine materials from space rocks |url=https://www.newscientist.com/article/2259373-asteroid-munching-microbes-could-mine-materials-from-space-rocks/ |access-date=9 December 2020 |work=New Scientist}}</ref><ref>{{cite journal |last1=Cockell |first1=Charles S. |last2=Santomartino |first2=Rosa |last3=Finster |first3=Kai |last4=Waajen |first4=Annemiek C. |last5=Eades |first5=Lorna J. |last6=Moeller |first6=Ralf |last7=Rettberg |first7=Petra |last8=Fuchs |first8=Felix M. |last9=Van Houdt |first9=Rob |last10=Leys |first10=Natalie |last11=Coninx |first11=Ilse |last12=Hatton |first12=Jason |last13=Parmitano |first13=Luca |last14=Krause |first14=Jutta |last15=Koehler |first15=Andrea |date=10 November 2020 |title=Space station biomining experiment demonstrates rare earth element extraction in microgravity and Mars gravity |url= |journal=Nature Communications |volume=11 |issue=1 |page=5523 |bibcode=2020NatCo..11.5523C |doi=10.1038/s41467-020-19276-w |issn=2041-1723 |pmc=7656455 |pmid=33173035 |last16=Caplin |first16=Nicol |last17=Zuijderduijn |first17=Lobke |last18=Mariani |first18=Alessandro |last19=Pellari |first19=Stefano S. |last20=Carubia |first20=Fabrizio |last21=Luciani |first21=Giacomo |last22=Balsamo |first22=Michele |last23=Zolesi |first23=Valfredo |last24=Nicholson |first24=Natasha |last25=Loudon |first25=Claire-Marie |last26=Doswald-Winkler |first26=Jeannine |last27=Herová |first27=Magdalena |last28=Rattenbacher |first28=Bernd |last29=Wadsworth |first29=Jennifer |last30=Craig Everroad |first30=R. |last31=Demets |first31=René}} 50x50px Available under CC BY 4.0.</ref><ref name=":82" /> Bioleaching in space also shows promise for application in building biological life support systems (BLSS).<ref name=":82" /> 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.<ref name=":82" />

{{multiple image | footer = | image1 = The BioRock Experimental Unit of the space station biomining experiment that demonstrated rare earth element extraction in microgravity and Mars gravity.webp | width1 = 200 | alt1 = BioRock Experimental Unit of the space station biomining experiment | caption1 = The experimental unit of the experiment | image2 = Effects of microorganisms on rare earth element leaching.webp | width2 = 128 | alt2 = Effects of microorganisms on rare earth element leaching | caption2 = ''S. desiccabilis'' is a microorganisms that showed high efficacy }}

=== Fungi in biomining === Fungi and plants (phytoextraction also known as phytomining) may also be used.<ref>{{cite journal |author=V. Sheoran, A. S. Sheoran & Poonam Poonia |date=October 2009 |title=Phytomining: A Review |journal=Minerals Engineering |volume=22 |issue=12 |pages=1007–1019 |bibcode=2009MiEng..22.1007S |doi=10.1016/j.mineng.2009.04.001}}</ref> Species of filamentous fungi, specifically those in the genera of ''Aspergillus'' and ''Penicillium'' have been shown as effective bioleaching agents.<ref name=":92"/> Fungi have the ability to solubilize metals through acidolysis, redoxolysis and chelation reactions.<ref name=":92" /> Like bacteria, fungi have been studied for their ability to extract rare earth elements and to process low grade ore. But their most promising and studied usage is in the breakdown of E-waste and the recovery of valuable metals from it, like gold.<ref name=":92" /><ref>{{Citation |last1=Bindschedler |first1=Saskia |title=Fungal Biorecovery of Gold From E-waste |date=2017 |journal=Advances in Applied Microbiology |pages=53–81 |publisher=Elsevier |doi=10.1016/bs.aambs.2017.02.002 |isbn=978-0-12-812050-7 |last2=Vu Bouquet |first2=Thi Quynh Trang |last3=Job |first3=Daniel |last4=Joseph |first4=Edith |last5=Junier |first5=Pilar|volume=99 |pmid=28438268 }}</ref> Despite the promise of fungal bioleaching, there has been no industrial applications of it as it does not out compete its bacterial counterparts.<ref name=":92" />

Fungi can be grown on many substrates, such as electronic scrap, catalytic converters, and fly ash from municipal waste incineration. Experiments have shown that two fungal strains (''Aspergillus niger, Penicillium simplicissimum'') were able to mobilize Cu and Sn by 65%, and Al, Ni, Pb, and Zn by more than 95%. ''Aspergillus niger'' can produce some organic acids such as citric acid. This form of leaching does not rely on microbial oxidation of metal but rather uses microbial metabolism as source of acids that directly dissolve the metal.<ref>{{cite journal|last1=Dusengemungu|first1=Leonce|last2=Kasali|first2=George|last3=Gwanama|first3=Cousins|last4=Mubemba|first4=Benjamin|title=Overview of fungal bioleaching of metals|journal=Environmental Advances|volume=5|issue=2021|article-number=100083 |publisher=Elsevier Ltd.|date=27 June 2021|language=EN|issn=2666-7657|doi=10.1016/j.envadv.2021.100083|doi-access=free|bibcode=2021EnvAd...500083D }}</ref>

== Economic feasibility and potential drawbacks == As a complement to traditional mining, biomining allows for extraction of some low-grade ore and mine tailings.<ref name=":132">{{Cite journal |last1=Martínez-Bellange |first1=Patricio |last2=von Bernath |first2=Diego |last3=Navarro |first3=Claudio A. |last4=Jerez |first4=Carlos A. |date=January 2022 |title=Biomining of metals: new challenges for the next 15 years |journal=Microbial Biotechnology |language=en |volume=15 |issue=1 |pages=186–188 |doi=10.1111/1751-7915.13985 |issn=1751-7915 |pmc=8719796 |pmid=34846776}}</ref> The approach is environmentally appealing,<ref>{{Cite web |title=Mission 2015: Bioleaching |url=https://web.mit.edu/12.000/www/m2015/2015/bioleaching.html |access-date=2024-01-21 |website=web.mit.edu}}</ref><ref>{{Cite journal |last1=Putra |first1=Nicky Rahmana |last2=Yustisia |first2=Yustisia |last3=Heryanto |first3=R. Bambang |last4=Asmaliyah |first4=Asmaliyah |last5=Miswarti |first5=Miswarti |last6=Rizkiyah |first6=Dwila Nur |last7=Yunus |first7=Mohd Azizi Che |last8=Irianto |first8=Irianto |last9=Qomariyah |first9=Lailatul |last10=Rohman |first10=Gus Ali Nur |date=2023-10-01 |title=Advancements and challenges in green extraction techniques for Indonesian natural products: A review |journal=South African Journal of Chemical Engineering |volume=46 |pages=88–98 |doi=10.1016/j.sajce.2023.08.002 |issn=1026-9185|doi-access=free }}</ref> however the Finnish Talvivaara project proved to be environmentally and economically disastrous.<ref>{{Cite news|title=Four charged in Talvivaara toxic leak case|url=https://yle.fi/uutiset/osasto/news/four_charged_in_talvivaara_toxic_leak_case/7485070|date=22 September 2014|publisher=Yle}}</ref><ref>{{cite journal |last1=Sairinen |first1=Rauno |last2=Tiainen |first2=Heidi |last3=Mononen |first3=Tuija |title=Talvivaara mine and water pollution: An analysis of mining conflict in Finland |journal=The Extractive Industries and Society |date=July 2017 |volume=4 |issue=3 |pages=640–651 |doi=10.1016/j.exis.2017.05.001 |bibcode=2017ExIS....4..640S |s2cid=134427827 }}</ref>

== See also == {{Portal|Biology|Technology}} * Bacterial oxidation * metallurgy * biotechnology * Phytomining * Phytoextraction * Bioremediation * Bioleaching

== Further reading == *Kundu et al. 2014 [http://www.hindawi.com/journals/jmin/2014/290275/ "Biochemical Engineering Parameters for Hydrometallurgical Processes: Steps towards a Deeper Understanding"] * ''T. A. Fowler and F. K. Crundwell'' – "Leaching of zinc sulfide with Thiobacillus ferrooxidans" * ''Brandl H.'' (2001) "Microbial leaching of metals". In: Rehm H. J. (ed.) ''Biotechnology'', Vol. 10. Wiley-VCH, Weinheim, pp.&nbsp;191–224 *{{cite journal | doi = 10.1016/j.hydromet.2006.05.001 | title = The bioleaching of sulphide minerals with emphasis on copper sulphides — A review | year = 2006 | last1 = Watling | first1 = H. R. | journal = Hydrometallurgy | volume = 84 | issue = 1–2 | page = 81| bibcode = 2006HydMe..84...81W }} *{{cite journal | doi = 10.1007/s00253-003-1404-6 | title = Bioleaching review part B | year = 2003 | last1 = Olson | first1 = G. J. | last2 = Brierley | first2 = J. A. | last3 = Brierley | first3 = C. L. | journal = Applied Microbiology and Biotechnology | volume = 63 | issue = 3 | pages = 249–57 | pmid = 14566430| s2cid = 24078490 }} *{{cite journal | doi = 10.1007/s00253-003-1448-7 | title = Bioleaching review part A | year = 2003 | last1 = Rohwerder | first1 = T. | last2 = Gehrke | first2 = T. | last3 = Kinzler | first3 = K. | last4 = Sand | first4 = W. | journal = Applied Microbiology and Biotechnology | volume = 63 | issue = 3 | pages = 239–248 | pmid = 14566432| s2cid = 25547087 }} *{{cite journal|last1=Qiu|first1=Guanzhou|last2= Li|first2=Qian|last3=Yu|first3=Runlan|last4=Sun|first4=Zhanxue|last5=Liu|first5= Yajie|last6=Chen|first6=Miao|last7=Yin|first7=Huaqun|last8=Zhang|first8=Yage|last9=Liang|first9=Yili|last10=Xu|first10=Lingling|last11=Sun|first11=Limin|date=April 2011|title=Column bioleaching of uranium embedded in granite porphyry by a mesophilic acidophilic consortium|journal=Bioresource Technology|volume=102|issue=7|pages=4697–4702|doi=10.1016/j.biortech.2011.01.038|pmid=21316943|last12=Liu|first12=Xueduan|bibcode=2011BiTec.102.4697Q }} == External links == * [http://www.isb.vt.edu/news/1994/news94.Jun.txt "NBIAP News Report."] U.S. Department of Agriculture (June 1994).

==References== {{reflist}}

Category:Biotechnology Category:Economic geology Category:Metallurgical processes Category:Applied microbiology Category:Metallurgy Category:Mining techniques