Biological leaching or bio-oxidation
was pioneered in copper mining and has been adapted for gold. It is a low temperature,
aqueous method of treating refractory sulphide ore
through pre-treatment with bacterial cultures. The bacteria catalyse the oxidation
of the ore.
The activity is stimulated
within process tanks known as bio-reactors, in which temperature, oxygen and nutrients
create the right conditions for the micro-organisms to flourish. Only naturally
occurring strains of bacteria are currently used but in the future genetically
engineered bacteria may be developed.
One of the most recent projects
is Newmont Mining’s bio-leach facility at its Carlin operations in Nevada, USA.
See also Heap Leaching.