The local MINERA ESCONDIDA, a subsidiary of a consortium headed by BHP BILLITON of Australia, recently completed an environmental study for a planned bioleaching project at its open-pit copper mine. Operating plans envision leaching low-grade sulfide ores containing 0.3% to 0.7% copper. Once leached, the material will be converted into copper cathodes using solvent-extraction at 2 new plants and electrowinning at another new unit.

According to a BHP BILLITON spokesman, the sulfide-leaching project would require an investment of about $500,000,000 to enable initially producing 84,000 tons per year (t/y) of copper cathodes. Longer-term ...