Geothermal places #18 on the Drawdown list of climate solutions. If it could increase its share of global electricity generation from 0.66 to 4.9% by 2050, geothermal would prevent 16.6 gigatons of CO2 emissions, at a net cost of $US155.5 billion but net savings of $US 1.02 trillion.
As its name implies, geothermal means “earth heat,” and the planet is plenty hot thanks largely to “ongoing radioactive decay of potassium, thorium, and uranium isotopes in the crust and mantle,” Drawdown reports. All told, “the heat energy generated is about 100 billion times more than current world energy consumption.” But to date, “only six to 7% of the world’s potential geothermal has been tapped,” mostly in geologically active regions like Iceland and Kenya, where traditional geothermal using natural hydrothermal reservoirs has long been used.
New approaches like enhanced geothermal systems (EGS), which uses engineering techniques like hydro-fracturing to inject high-pressure water into areas that “contain ample heat but no water,” could “dramatically increase the geographic reach of geothermal energy”—in theory. But the “up-front costs of drilling are especially steep, particularly in less certain, more complex environments,” which means public investment will be the key increasing geothermal output. [A technique that relies on fracking will also run into some of the fierce worries and objections that have accompanied the natural gas fracking boom, beginning with increased earthquake activity nearby. –Ed.]
Geothermal also faces its share of health and environmental challenges. Whether it is “naturally occurring or pumped in, water and steam can be laced with dissolved gases, including carbon dioxide, and toxic substances such as mercury, arsenic, and boric acid.” And “though its emissions per megawatt- hour are just five to 10% of a coal plant’s, geothermal is not without greenhouse impact.”
But Drawdown notes that geothermal can still deliver huge amounts of either baseload or dispatchable power. “Theoretical projections based on geologic surveys of Iceland and the United States indicate that undiscovered geothermal resources could supply one to two terawatts of power, or seven to 13% of current human consumption.”
Even as innovations like EGS advance, “continued development of traditional geothermal remains indispensable,” the chapter notes, “especially in Indonesia, Central America, and East Africa—places where the planet is most active and ‘earth heat’ is abundant.”