Review on life cycle environmental effects of geothermal power generation

A comprehensive overview of potential environmental effects during the life cycle of geothermal power plants is presented using widely scattered available information from diverse literature sources. It is shown that so far only few studies provide quantitative estimates on both direct and indirect environmental consequences. Life cycle assessment (LCA) studies on geothermal electricity production are scarce and typically country- or site-specific with a focus on the geothermal fields in the western USA. In fact a general assessment is challenging due to the dissimilar nature and maturity of currently applied geothermal power plants, the influence of site-specific characteristics, and uncertainty in long-term productivity. Especially life cycle fugitive emissions, the thread from geological hazards, and water and land use effects are highly variable and may even change with time. Based on our survey, ranges are provided for emissions and resource uses of current worldwide geothermal power generation. We also define an approximate universal case that represents an expected average. The collected data is suitable to feed life cycle inventories, but is still incomplete. Potential emissions of critical toxic substances such as mercury, boron and arsenic and their local and regional environmental consequences are particularly inadequately addressed on the global scale.