The Safford Leaching group is pursuing value with a new technique that could accelerate copper recovery from stacked ore and squeeze more copper out of older leach pad cells. The Leach to the Last Drop strategy involves blanketing a leach pad section with clear plastic sheeting, which traps solar heat — like a greenhouse — and warms the pad surface. Other Freeport-McMoRan sites that have tried it have seen a 1 percent increase in copper recovery for every degree (Celsius) of increase in pad surface temperature. That is significantly more copper each day.
Crews already have overlaid a portion of the Safford pad and now are blanketing part of the Lone Star pad. They coordinate their work with the drip line crew, so drip line pulling stays ahead of the plastic installation. It takes 10 employees approximately 30 minutes to roll out each 40-ft.-by-400-ft. section of material, and securing the plastic to the pad takes up to seven hours. It also requires a lot of patience, because even the slightest wind makes proper installation a challenge.
Our Leaching employees have embraced this project as their own and are committed to its success. They meet with leadership weekly to provide updates, share new ideas and get support for making improvements to the process. If the blanketing method is successful, it could help relieve some of the burden on Mining and Crush and Convey to maintain a high level of ore delivery to the Lone Star pad. As we determine what our best day of blanketing looks like, we will share that information with all Freeport sites.