Solution for accessing deep deposits

The process

The BIOMOre objective is to develop advanced technological concepts for the in-situ recovery of metals from deep deposits using a combination of channeling and bioleaching. The methods and procedures will be designed, evaluated and optimized using laboratory experiments, numerical simulations and modeling. A holistic characterization of the geological conditions will complement this work and allow the identification of suitable deposits for in-situ bioleaching.

These optimized methods will then be applied in a closed underground test using a block of approximately 100 m3 at the Rudna Mine of KGHM Polska Miedz, Poland. As the mine has already been excavated to depth, the use of this site avoids the need to drill down from the surface. The experimental field site comprises all necessary systems for controlling the process and monitoring possible environmental impacts. No harmful substances will remain in the channeled orebody after the activities have been completed.

The environmental, social and geological impacts of the in-situ bioleaching process will be evaluated, and the process design will be critically assessed in a feasibility study to ensure that it can be implemented profitably at industrial scale. However, this potential pilot plant is not part of the currently running project.

Schematic representation of in situ indirect bioleaching of a deep-buried copper sulfide ore.
© DMT GmbH & Co. KG/Germany

An acidic, ferric iron-rich lixiviant is generated in a bioreactor (containing microorganisms that catalyse iron oxidation at low pH) located at the land surface. This solution is injected through boreholes to the ore body (typically at 1 – 1.5 km depth) which has previously been fractured to open channels through which the lixiviant flows. Ferric iron oxidises the sulfide minerals in the ore body, generating an increasingly ferrous iron- and copper-enriched solution, the dissolved metals being retained in solution by the low pH. This “pregnant leach solution” is pumped to the land surface, and the target metal (copper) extracted using one of several available methods (e.g. solvent extraction or sulfide precipitation). The ferrous iron-rich raffinate liquor produced is passed through the bioreactor to regenerate ferric iron, and the re-oxidised lixiviant recirculated into the ore body to continue the extraction process.