Extraction of energy from a geothermal system at a rate at which the energy source is renewed on a timeframe similar to that of biomass and hydro-electricity would mean than only extremely small developments could proceed. Much of the resource would therefore not be available for extractive use by current generations and the next few generations.
To sustain the energy-producing potential of a geothermal system to meet the reasonably foreseeable needs of future generations, extraction must be conducted in a way and at a rate that can be maintained by those future generations. In order to maximize financial return, geothermal developers may seek to extract all the available energy within a consenting period of up to thirty-five years.
The principles of sustainable management applied to a geothermal system take into account a great deal more than the ability to extract particular amounts of heat and fluid over a particular period. They also require that the effects of the take and discharge of energy and fluid on the system and on other natural and physical resources be avoided, remedied, or mitigated. In addition, they take into account issues of economic efficiency.
Efficient use of energy, includes several dimensions: productive efficiency (output at a low cost); allocative efficiency (allocating resources to production that society values the most); and dynamic or innovative efficiency (where technological change is encouraged and used to produce productivity gains). Wasteful take and discharge lead to greater loss of heat and fluid than is required for the purpose. This is inconsistent with sustainable management and the principle of productive efficiency. Wasteful use can also occur, with geothermal resources being used in the place of more appropriate sources of heat, water, or minerals. This can deprive current and future generations of the ability to use the resource appropriately, and is inconsistent with the principle of allocative efficiency..............
