Refractory gold ore processing by bacterial biooxidation (BIOX® and similar tank bioleaching) — instead of roasting; with biological cyanide destruction of tailings water
Roasting of arsenopyrite/pyrite gold concentrates (emissions of SO2 and arsenic trioxide), partly pressure oxidation (energy-intensive); chemical cyanide destruction (partly)
Refractory sulfide gold deposits (Russia: Krasnoyarsk, Yakutia, Far East, Kazakhstan; also Africa, Australia, China)
Suppliers 4
| Mintek | South Africa | active |
| BacTech Environmental | Ecuador | active |
| Universal Bio Mining, LLC | United States | active |
| Metso | Finland | active |
Route into Russia / EAEU SERV
- Regulator
- — (operator: Rosprirodnadzor, Rostechnadzor)
- Typical time
- none for the service; operator permits (integrated environmental permit ~1 month)
- Legal basis
- No product registration; operators of category I facilities need an integrated environmental permit (Federal Law 7-FZ Art. 31.1) and, where relevant, Rostechnadzor licences
Information, not legal advice — confirm the procedure for your product.
Proof 8 claims
Roasting (and pressure oxidation)
Bacterial biooxidation (e.g., BIOX process)
- Displaced at scale?
- partly
- Caveats
- Bio-leaching is currently the process of choice for only 20% of the refractory gold treatment plants worldwide.
- Hand review
- D2 Bacterial oxidation chosen for 22 of the ~40 refractory-gold plants built since 1986 (vs 9 roasting, 9 pressure oxidation; SAIMM); ~20% of all refractory gold plants worldwide (journal).
- checked
- 2026-10-06
| The BIOX process has been in commercial operation for over 20 years and is a mature, worldwide recognized technology for the pretreatment of refractory gold concentrates. “The BIOX® process for the pretreatment of refractory gold concentrates has been in commercial operation for the last 20 years.” global · 2009 · minority but measured share or volume | industry association saimm.co.za |
| Compared to roasting, bio-leaching can generally reduce capital costs by 12–20%, operating costs by 10% in some cases, and construction time by 25%. “Compared to roasting, bio-leaching can generally reduce capital costs by 12–20%, operating costs by 10% in some cases, and construction time by 25%.” global · 1995 · not applicable | peer-reviewed ✓ www.journalssystem.com |
| Bio-leaching is currently the process of choice for only 20% of the refractory gold treatment plants worldwide. “In spite of numerous advantages of bacterial leaching, it is currently the process of choice for only 20% of the refractory gold treatment plants worldwide.” global · 1995 · minority but measured share or volume | peer-reviewed ✓ www.journalssystem.com |
| Biooxidation does not require high energy consumption and complex equipment, and allows one to avoid toxic gas emissions when arsenic-containing concentrates are processed. “STRB has some advantages over other technologies (roasting, pressure oxidation); it does not require high energy consumption and complex equipment, and allows one to avoid toxic gas emissions when arsenic-containing concentrates are processed [1,2,3,4,5].” global · 2024 · not applicable | peer-reviewed pmc.ncbi.nlm.nih.gov |
| Since 1986, 22 bacterial oxidation plants have been built, compared to 9 roasting plants and 9 pressure oxidation plants. “Number of refractory gold plants built since 1986: Roasting – 9 Pressure Oxidation – 9 Bacterial Oxidation - 22” global · 1986-2015 · large measured reduction of the old process | industry association ✓ www.saimm.co.za |
| Bio-oxidation plants produce approximately 5% of the total mine gold globally. “They produce approximately 5% of the total mine gold by bio-oxidation process [10] .” global · current · minority but measured share or volume | peer-reviewed ✓ exa.ai |
| In 2020, BIOX plants produced approximately 1.1 million ounces of gold, equivalent to 0.9% of global gold production. “Approximately 1.1 million ounces was produced by BIOX ® plants in 2020, equivalent to 0.9% of global gold production that year.” global · 2020 · minority but measured share or volume | peer-reviewed ✓ link.springer.com |
| Polyus reported production of over 30 tonnes of gold through the BIONORD process at Olimpiada in 2019, representing about 0.83% of global gold production that year. “Polyus reported production of over 30 tonnes of gold through the BIONORD process at Olimpiada in 2019, representing about 0.83% of global gold production that year.” Russia · 2019 · minority but measured share or volume | peer-reviewed ✓ link.springer.com |
References 3
- van Aswegen PC, van Niekerk J, Olivier W (2007). The BIOX™ process for the treatment of refractory gold concentrates. In: Rawlings DE, Johnson DB (eds) *Biomini NOT CHECKED — regulation …
- Rawlings DE, Johnson DB (2007). The microbiology of biomining: development and optimization of mineral-oxidizing microbial consortia. *Microbiology* 153: 315–32 VERIFIED DOI · cited by 387
- Brierley CL, Brierley JA (2013). Progress in bioleaching: part B: applications of microbial processes by the minerals industries. *Applied Microbiology and Biot VERIFIED DOI · cited by 331
Details
Replaces: roasting of arsenical gold concentrates · Scope: gold mining · Evidence: high
The chemical problem#
In refractory ores, gold is locked inside pyrite and arsenopyrite. The classic treatment is roasting, which releases SO₂ and arsenic trioxide. The Giant Mine (Yellowknife, Canada) left about 237,000 t of arsenic trioxide dust stored underground, a remediation liability costing more than 1 billion Canadian dollars.
Product overview#
Biooxidation uses acidophilic iron- and sulfur-oxidizing microorganisms (Acidithiobacillus ferrooxidans, A. thiooxidans, Leptospirillum ferriphilum, Sulfobacillus, Ferroplasma) in stirred, aerated tanks at 35–45 °C. They dissolve the sulfide matrix and release the gold for cyanidation. Arsenic ends up as stable ferric arsenate precipitate instead of airborne As₂O₃.
- BIOX® (Gencor/Gold Fields, now Outotec/Metso): commercial since 1986 (Fairview mine, South Africa).
- Olimpiada (Polyus, Krasnoyarsk Krai, Russia) runs one of the world’s largest biooxidation plants. Other plants include Suzdal (Kazakhstan), Fosterville (Australia) and several in China and Africa.
- Biological cyanide destruction: at the Homestake mine (South Dakota, USA), rotating biological contactors degraded cyanide and thiocyanate in mill effluent from 1984, an early industrial example.
Active ingredient / Composition#
Mixed cultures of mesophilic/moderately thermophilic acidophiles, air, nutrients (N, P, K), and limestone for neutralization.
Key facts#
| Parameter | Value |
|---|---|
| Class | Industrial biohydrometallurgy |
| Residence time | About 4–6 days in tanks |
| Gold recovery | Typically above 90 % after biooxidation + cyanidation (ore-dependent) |
| Arsenic fate | Ferric arsenate precipitate (much more stable than As₂O₃ dust) |
| Air emissions | No SO₂/As₂O₃ stack emissions |
Advantages#
- Eliminates roaster emissions of SO₂ and arsenic.
- Lower capital cost than pressure oxidation for moderate plant sizes.
- Robust, self-regenerating microbial cultures; a proven Russian industrial capability.
Mode of action#
Microbes oxidize Fe²⁺ → Fe³⁺ and reduced sulfur → sulfate. Ferric iron chemically attacks the sulfide minerals (indirect leaching), which destroys the mineral lattice holding the gold.
Application#
| Ore/stream | Measure | Specifics |
|---|---|---|
| Refractory sulfide concentrate | Tank biooxidation → CIL cyanidation | Temperature control, oxygen supply |
| Low-grade ore | Heap biooxidation (e.g. Newmont Carlin-type) | Slower, lower cost |
| Cyanide/thiocyanate effluents | Biological treatment (RBCs, activated sludge), then polishing | Complements chemical destruction |
Limitations#
- Cyanide is still used after biooxidation (thiosulfate leaching is an emerging alternative).
- Needs cooling (exothermic) and oxygen supply; carbonaceous ores (“preg-robbing”) need extra steps.
- Neutralization residues must be stored safely.
Evidence of displacement — D2: measurable displacement (minority share)#
Assessment (hand-reviewed): Bacterial oxidation chosen for 22 of the ~40 refractory-gold plants built since 1986 (vs 9 roasting, 9 pressure oxidation; SAIMM); ~20% of all refractory gold plants worldwide (journal).
Figures found (verified as quoted, but the assessment above explains why they do not count as displacement evidence for this substitution):
- displacement — Bio-leaching is currently the process of choice for only 20% of the refractory gold treatment plants worldwide. (global, 1995; peer-reviewed: journalssystem.com)
- displacement — Since 1986, 22 bacterial oxidation plants have been built, compared to 9 roasting plants and 9 pressure oxidation plants. (global, 1986-2015; industry association: saimm.co.za)
- performance — Bio-oxidation plants produce approximately 5% of the total mine gold globally. (global, current; peer-reviewed: exa.ai)
- performance — In 2020, BIOX plants produced approximately 1.1 million ounces of gold, equivalent to 0.9% of global gold production. (global, 2020; peer-reviewed: link.springer.com)
Suppliers — real products and services (from the vendor index)#
Honest finding (updated 2026-09-30): the index now has one biometallurgy service supplier — Mintek (tank and heap bioleaching). No supplier yet names a licensed BIOX-type refractory-gold plant operator; BacTech Environmental has the BACOX/Zero-Tailings process for exactly this duty but is development-stage and pre-revenue, so it is deliberately not cited while its financing closes.
Companies below are active vendors in the vendor index whose own card (profile / official website) shows this product or service — matched 2026-09-30 by keyword and checked by hand against the card text. Being listed is not an endorsement; open each card for evidence, contacts and status.
Update 2026-10-02: the new USA & Canada dataset supplies this product — rows marked NA below. For Africa/ME, LatAm and Asia the regional gap noted above still stands.
Update 2026-10-05: the new Europe dataset supplies this product — rows marked Europe below. For the other regions the gap noted above still stands unless a row says otherwise.
| Company | Region · Country | What the index shows | Card |
|---|---|---|---|
| Mintek | Africa/ME · South Africa | tank and heap bioleaching; biometallurgy (microorganism-assisted metal recovery); gold among priority commodities | card |
| BacTech Environmental | NA · Canada | BACOX bioleaching of refractory ores and toxic mine waste | card |
| Universal Bio Mining, LLC | NA · United States | bioleaching processes for gold and copper | card |
| Metso | Europe · Finland | BIOX bio-oxidation process for pre-treatment of refractory gold ores | card |
Government funding signals#
Public grants for a specific technology are a leading indicator: governments fund what regulators want to replace and what is close to practical adoption. Searched on 2026-09-27 in: EU CORDIS (FP7, Horizon 2020, Horizon Europe), US federal awards (USAspending: USDA NIFA/ARS/APHIS/Forest Service, EPA, DOE, NOAA, USAID; plus NSF and NIH), UK UKRI Gateway to Research, Australian Research Council. Each grant below was reviewed by hand for relevance. China, Brazil and India are covered in the subsection below (publication-acknowledged grants). Not covered: Russia (RSF, FASIE — not reachable from the research environment) and national agencies outside these databases. Amounts are the funder’s contribution as recorded (US NIH/UKRI: per award or fiscal year).
Signal: Strong. 3 relevant grant(s) · about €9.7M in total · jurisdictions: EU, USA.
| Funder / programme | Project | Lead organisation | Start | Amount | Link |
|---|---|---|---|---|---|
| European Commission — H2020 RIA | BioMOre: New Mining Concept for Extracting Metals from Deep Ore Deposits using Biotechnology | Kghm Polska Miedz Sa (PL) | 2015 | 8,564,962 EUR | link |
| US federal — Department of the Air Force | Tas::57 3600::tas “novel heavy metal biooxidation mechanisms in extremely thermoacidophilic archaea” | North Carolina State University (US) | 2013 | 1,026,976 USD | link |
| US NSF — STTR Phase I | STTR Phase I: Engineering Alternative Oxidation Activity in A. ferrooxidans For Enhanced Biohydrometallurgy Capabilities | Ironic Chemicals Llc (US) | 2018 | 225,000 USD | link |
China, Brazil, India — national research grants acknowledged in publications#
Chinese, Brazilian and Indian funders have no open grant databases reachable here, so this measures scientific papers published since 2015 that acknowledge national government grants, taken from the grant numbers publishers deposit with Crossref. Only papers whose title contains this article’s key terms are counted (a conservative lower bound; “100+” = search window full). It shows research-funding intensity, not budgets. Funders: China — NSFC, National Key R&D Program, China Agriculture Research System; Brazil — CNPq, CAPES, FAPESP, Embrapa, FAPEMIG; India — DBT, DST, ICAR, SERB, CSIR, BIRAC. Rating per country: Strong ≥50 papers · Moderate 10–49 · Weak 1–9.
| Country | Papers funded (2015–2026) | Signal | Main funders (grant acknowledgements) | Example grant → funded paper |
|---|---|---|---|---|
| China | 48 | Moderate | NSFC (59), National Key R&D Program (11) | National Key R&D Program 2022YFC2105302 → Biooxidation of FeS2 and FeAsS in refractory gold ores: A comparative study of aeration in stirred tank… (2026) doi |
| Brazil | 0 | None | – | – |
| India | 0 | None | – | – |
Scientific evidence#
- van Aswegen PC, van Niekerk J, Olivier W (2007). The BIOX™ process for the treatment of refractory gold concentrates. In: Rawlings DE, Johnson DB (eds) Biomining. Springer, Berlin.
- Rawlings DE, Johnson DB (2007). The microbiology of biomining: development and optimization of mineral-oxidizing microbial consortia. Microbiology 153: 315–324.
- Brierley CL, Brierley JA (2013). Progress in bioleaching: part B: applications of microbial processes by the minerals industries. Applied Microbiology and Biotechnology 97: 7543–7552.
Bioeconomy value#
Microorganisms replace high-temperature roasting in a heavy industry, avoiding toxic air emissions, and give Russia a globally leading biotech application.