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Geothermal Results – Life Cycle Assessment Review

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Chart that shows life cycle greenhouse gas emissions for geothermal technologies. For help reading this chart, please contact the webmaster.

Estimates of life cycle greenhouse gas emissions from geothermal power generation
Credit: Goldstein, B., G. Hiriart, R. Bertani, C. Bromley, L. Gutiérrez-Negrín, E. Huenges, H. Muraoka, A. Ragnarsson, J. Tester, V. Zui, 2011: Geothermal Energy. In IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation [O. Edenhofer, R. Pichs-Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schlömer, C. von Stechow (eds)], Cambridge University Press. Figure 4.6

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To better understand geothermal power systems, NREL completed a comprehensive review and analysis of life cycle assessments on flash steam and enhanced geothermal systems (EGS) published between 1980 and 2010.

The figure below shows the results of the review and analysis of published life cycle assessments on geothermal electricity generation passing screens for quality and relevance. Life cycle assessments estimate that full life cycle CO2-equivalent emissions for geothermal energy technologies are less than 50 g CO2eq/kWhe for flash steam geothermal power plants and less than 80 g CO2eq/kWhe for projected EGS power plants.

Although few geothermal studies are available for review, these findings suggest that greenhouse gas emissions for geothermal technology are small relative to those of coal-fired electricity generation. Additional geothermal life cycle assessments are needed to better understand sources of variability and to corroborate the results published to date.