### The Ore Grade and Depth Influence on Copper Energy Inputs ...

Nov 22, 2016 · This warrants the first conclusion: Statistically Eq. ( 4) is the best model for mines with milling/flotation. On the basis of this, an ore grade of, and % at 300 m of depth results in an energy cost of 60, 127 and 447 MJ/kg for underground mines, and 52, 95 and 255 MJ/kg for surface mines, respectively.