As the copper resource is developed, mining begins by extracting ore closest to the surface. As these resources are removed, equipment must mine ore from an increasing depth. Deeper pits result in longer, uphill hauls for trucks to deliver ore to the mill for processing — increasing diesel consumption, which results in greater energy consumption and GHG emissions.
In addition, to enhance project economics, higher grade ore is commonly processed early in the mine life, followed by lower grade ore. For example, Teck’s Highland Valley Copper Operations were processing ore with a copper grade of 0.47% in 1988; this had declined to a grade of 0.30% in 2012. Decreasing ore grades mean that greater amounts of material must be moved and processed to achieve the same quantity of final product.
This combination of increased haul distances and decreasing ore grades increases energy consumption and GHG emissions required to produce each tonne of product over the life of a mine.