“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 – It is green: When coal is used to produce an equivalent amount of energy, the CO2 emissions are 35 times greater, according to information from the NREL. Emissions from geothermal power plants contain mostly water vapour and they do not emit particulates, hydrogen sulphide or nitrogen oxides.