NRE resources do not replenish (or produced) in a short period of time (it might take millions of years). Some of the NRE resources are coal, petroleum, natural gas and radioactive material (nuclear fuel).
It is undeniable that these resources produce high amount of usable energy via small volume but high dependence on resources that will deplete one day is not a good move.
One good step taken in managing NRE is the optimisation of processes as well as power generation efficiency. This will ensure higher yield of energy is obtained from these resources.
However, what will be our future fuel when these resources are depleted?