Fortunately, Bitcoin has a a way of aligning incentives in the case of energy consumption. Mining is a very low margin business, because of this, we have seen a centralization of energy in areas with cheap (or even free) energy. Right now green energy (hydro, solar, wind) aren't the cheapest way of producing energy, it is still much cheaper to burn coal/natural gas, however, someday green energy will be a much more cost effective way of producing energy. When that happens we will definitely see more mining operations utilizing green energy to maximize their small margin for profits.