Greenhouse Gases from Geothermal Power Production

Abstract

Geothermal is a renewable source energy that can be used directly for heating or for power production. Geothermal utilization, particularly power production, may result in some greenhouse gas (GHG) emissions. GHG emissions from geothermal power production is generally small in comparison to traditional base load thermal energy power generation facilities. This is mainly due to the fact that the large majority of installations draw their geothermal energy from geothermal reservoirs with low GHG concentrations. However, as the geothermal sector has expanded, a wider range of geothermal resources have been brought into exploitation, including geothermal systems with relatively high GHG concentrations in the reservoir fluid. There is a growing realization within the geothermal community that geothermal power plants can, in rare instances, release significant quantities GHG into the atmosphere. This interim technical note presents an overview of the current knowledge on GHG emissions from geothermal systems and geothermal power plants, and gives guidance on how to assess GHG emissions from geothermal projects when this is required, depending on their stage of development. This note identifies critical knowledge gaps and presents recommendations as to how close these gaps and proposes an interim methodology to estimate GHG emissions from geothermal projects that financing institutions, such as the World Bank, intend to support. The plan is to update this note when the methodology has been tested by application to actual projects and some of the current knowledge gaps have been closed as more information become available. This note proposes a way to estimate future emission factors for geothermal projects under development. For instance, if a pumped binary power plant is planned, the emission factor will be 0. Projects using other energy conversion technologies will result in some emissions. For projects where wells have been drilled and tested, formulas are provided to compute emission factors based on the chemical composition of the geothermal fluid and the design parameters of the power plant. For projects located in the vicinity of existing power plants in analogous geologic settings, emission factors from the existing plants can be used.