Demand for raw materials is increasing exponentially. To satisfy that demand, more minerals need to be mined from the Earth’s crust. As a result, minerals are being exhausted and ore grades decline until values close to crustal concentration. Lower ore grade mines mean also more energy, which in turn entails fossil fuel emissions and more climate change, due to renewable energies are not introduced in this industry yet. This paper estimates the specific energy for concentration for the beneficiation process of metals lead and zinc as case studies. The evaluation has been performed with a specialized software, HSC Chemistry which assesses the specific energy for every stage: comminution, flotation, and refining. Different scenarios have been established to simulate the future behavior of a mine when it approaches depletion. Preliminary results show that energy consumption for lead would increase by 5 times when compared to the current situation if ore grades decrease until the level of tailings, while for zinc by almost 2.