Grand Prismatic Spring in Yellowstone National Park


© Inger Vandyke / VWPics / Redux


Yellowstone National Park in the USA is one of the first nature reserves established in the world and an unequalled natural wonder. This place unique in the world is also a pristine icon of all that the Earth has to offer in terms of geothermal energy, possessed by Yellowstone in sufficient quantities to provide the entire USA with electricity. This enormous amount of energy comes from the decay of radioactive isotopes beneath the Earth’s crust and from energy generated during formation of the planet, which flows to the surface via the convective motion of molten rock. It has been used since the Palaeolithic for direct heating, a purpose it still fulfils today, contributing more than 28 GW to the world’s heat requirements. Although geothermal energy cannot claim the title of “renewable”, it is considered almost inexhaustible with respect to the world’s energy needs and therefore represents a valid alternative to fossil fuels. Like fossil fuels and unlike renewable sources, it allows electricity with a constant power to be generated without interruption. However, although modern, these plants are not completely neutral in terms of environmental impact and although the release of any toxic elements is very limited, there is still an albeit very small emission of carbon dioxide. In addition, the water used in the plant has to be injected back into the ground and this can contribute to seismic events and subsidence, so not every area with economically viable characteristics is suitable for geothermal exploitation. In 2015 the world’s electricity production from geothermal sources amounted to a total of 12.8 GW, about 1% of the world’s needs; values that can certainly be sustainably increased.

Giulio Guggia