What is copper bioleaching and how does it work in mining?

Copper bioleaching is a metal extraction method that uses microorganisms to convert copper locked in rock into soluble copper ions that can be recovered as commercial product. In sulphide ores, chemolithoautotrophic microbes gain energy by oxidising iron and sulphur. Ferrous iron (Fe²⁺) is oxidised to ferric iron (Fe³⁺), which helps to break down minerals such as chalcocite and chalcopyrite, releasing copper into solution. Other microbes oxidise sulphur to generate sulphuric acid, keeping the pH low so copper stays dissolved. The copper-rich pregnant leach solution is then processed, commonly via solvent extraction and electrowinning (SX-EW) or by cementation using iron.

Which bacteria are used for copper bioleaching and why are indigenous microbes important?

Copper bioleaching commonly relies on acid-loving, heat-tolerant microbes, including thermophilic and mesophilic species that thrive in low pH environments. A frequently cited example is acidithiobacillus ferrooxidans, which supports the iron and sulphur chemistry that drives sulphide breakdown. Some operators prefer indigenous microorganisms already present at the site because they are naturally adapted to the local ore, temperature, water chemistry and acidity, which can improve resilience and stability during operations. In practice, success often comes less from trade secrets and more from know-how: selecting compatible microbial communities, maintaining the right conditions and tuning nutrients and process controls to keep leaching fast and consistent.

What is the difference between heap leaching and vat leaching for copper bioleaching?

Heap bioleaching places crushed copper ore on lined pads and irrigates it with a bio-lixiviant; dissolved copper percolates through the heap and is collected for processing. It is typically the lower-capex option, relatively straightforward to scale for large volumes of low-grade ore, and can start up quickly. However, recovery is usually around 70% to 90% and leaching can take months or even years. Vat leaching submerges crushed ore in tanks containing bio-lixiviant, keeping solids suspended so microbes can access the mineral surfaces. It tends to be faster, often days to weeks, and can achieve higher recoveries, but equipment and operating costs are higher.

Why is copper bioleaching adoption slow despite growing demand for critical minerals?

Adoption is slowed by long and variable leach times, high upfront capital in some configurations and a persistent perception that bioleaching is mainly for low-grade ores while high-grade material goes to smelting. Commercialisation can also stall inside large organisations: many companies trial bioleaching, but financing and internal decision-making may not follow. Profitability depends on ore grade, scale, recoverable by-products, and downstream processing routes, so a technically successful pilot does not automatically become a bankable project. Uptake is strongest where it extends mine life and monetises lower-grade resources, such as in Chile, while other regions remain cautious despite interest.

Where is copper bioleaching used worldwide, and what’s next for the global bioleaching market?

Copper bioleaching already contributes up to around a fifth of global copper production, with major adoption in Latin America and China. Chile, the world’s largest copper producer, has used bioleaching to make lower-grade ore profitable and extend mine life, while China has operated large-scale bioheapleaching at sites such as Zijinshan for decades. Major miners are also pushing new deployments, including Rio Tinto’s Nuton technology, which announced first copper production at Johnson Camp in Arizona in late 2025. Next growth is expected not only from copper ores but from wider biomining of industrial waste, tailings, e-waste and rare earth-bearing materials, where bioleaching can combine recovery with remediation and new revenue streams.