Argument: The environmental benefits of geothermal outweigh the costs
"A CLEAN ENERGY FUTURE FOR THE UNITED STATES: THE CASE OF GEOTHERMAL POWER". Testimony by the President of Iceland Olafur Ragnar Grimsson at a Senate Hearing Committee on Energy and Natural Resources". US Senate. 26 Sept. 2007 - PROS AND CONS OF GEOTHERMAL ENERGY ENVIRONMENTAL FRIENDLINESS
The Geothermal Energy Association has a wealth of information about geothermal energy. Here is a short environmental summary from the site.
Geothermal energy use does entail some environmental impact, but it is safe to say that the environmental benefits far outweigh the costs.
Most geothermal facilities operate virtually emission free. Some even reduce sulfur emissions that would have occurred from natural venting if these sites had been left untapped.
A few do produce some silica and sulfur dioxide, both of which are largely removed from the vapors and either returned to the hydrothermal well or processed and sold for industrial uses.
Almost 100% of the visible, airborne effluent seen rising from geothermal plants is water vapor.
Geothermal energy has the smallest land use of any major power generation technology. A typical geothermal facility occupies about the same space as a gas fired plant of the same capacity. But the geothermal facility does not require miles of buried pipeline to carry fuel to keep it running.
Geothermal facilities also have no coal or nuclear fuel to mine and transport, no radioactive wastes or ash wastes to deal with, and no emissions of carbon dioxide, particulates, or other combustion byproducts.
In other words, geothermal energy is one resource that can be universally celebrated for its contribution to a cleaner, safer environment.