Greenhouse-gas Emissions from Solar Electric- and Nuclear Power: A Life-cycle Study

Vasilis M. Fthenakis * and Hyung Chul Kim Energy Sciences and Technology Department, Bldg 475B, Brookhaven National Laboratory, Upton, NY 11973, U.S.A.; and Center for Life Cycle Analysis, Department of Earth and Environmental Engineering, Columbia University, New York, NY 11027 * Corresponding author. Tel.: +1-631-344-2830: fax: +1-631-344-7650. Email address: [email protected] ABSTRACT Solarand nuclear-electricity-generation technologies often are deemed “carbon-free” because their operation does not generate any carbon dioxide. However, this is not so when considering their entire lifecycle of energy production; carbon dioxide and other gases are emitted during the extraction, processing, and disposal of associated materials. We determined the greenhouse-gas emissions (GHG), namely, CO2, CH4, N2O, and chlorofluorocarbons due to materials and energy flows throughout all stages of the life of commercial technologies for solar-electricand nuclear-power-generation, based on data from 12 photovoltaic (PV) companies, and reviews of nuclear-fuel life cycles in the United States, Europe, and Japan. Previous GHG estimates vary widely, from 40 to 180 CO2-eq./kWh for PV, and 3.5 to 100 CO2-eq./kWh for nuclear power. Country-specific parameters account for many of these differences, which are exacerbated by outdated information. We conclude, instead, that lifetime GHG emissions from solarand nuclearfuel-cycles in the United States are comparable under actual production conditions and average solar irradiation, viz., 22-49 g CO2-eq./kWh (average U.S.), 17-39 g CO2eq./kWh (South West) for solar electric, and 16-55 g CO2-eq./kWh for nuclear energy. However, several factors may significantly change this picture within the next five years, and there are unanswered questions about the nuclear fuel cycle that warrant further analyses.