Abstract
Geothermal energy could play a crucial role in the European energy market and future scenarios focused on sustainable development. Thanks to its constant supply of concentrated energy, it can support the transition towards a low-carbon economy. In the energy sector, the decision-making process should always be supported by a holistic science-based approach to allow a comprehensive environmental assessment of the technological system, such as the life cycle assessment (LCA) methodology. In the geothermal sector, the decision-making is particularly difficult due to the large variability of reported results on environmental performance across studies. This calls for harmonized guidelines on how to conduct LCAs of geothermal systems to enhance transparency and results comparability, by ensuring consistent methodological choices and providing indications for harmonized results reporting. This work identifies the main critical aspects of performing an LCA of geothermal systems and provides solutions and technical guidance to harmonize its application. The proposed methodological approach is based on experts’ knowledge from both the geothermal and LCA sectors. The recommendations cover all the life cycle phases of geothermal energy production (i.e., construction, operation, maintenance and end of life) as well as a selection of LCA key elements thus providing a thorough base for concerted LCA guidelines for the geothermal sector. The application of such harmonized LCA framework can ensure comparability among LCA results from different geothermal systems and other renewable energy technologies.
Highlights
Geothermal energy encompasses the energy derived from the Earth’s interior, be it in the form of electricity or heat
Results can range from 65 g CO2 eq/kWhe calculated by Frick and co-authors [19] to an average of 712.5 g CO2 eq/kWhe as reported by Bravi and Basosi [20]. Such a significant variation can be related to the different technology adopted by the investigated plants
Guidance is given on geothermal-specific parameters used as inputs in life cycle assessment (LCA), on choices in the life cycle inventories (LCI) data collection, and on modelling approaches and methodological assumptions resulting in the life cycle impact assessment (LCIA) and the interpretation and reporting of the study
Summary
Geothermal energy encompasses the energy derived from the Earth’s interior, be it in the form of electricity or heat. EGS rely on a technology similar to binary cycles except that the water availability or the host rock permeability is enhanced in a preliminary step [9] Such technological variability of geothermal systems, coupled with the peculiar geomorphological characteristics of the exploited geothermal reservoirs, result in a large range of energy outputs as well as potential environmental impacts. Handbook [16], developed by the Joint Research Center of the European Commission, is based on the primary definition and information given in the ISO 14,040 series and supplies more detailed methodological recommendations, supporting documents and tools These methodological frameworks provide general indications but do not account for specificities of energy pathways, and, of energy systems, leaving the user facing a large range of choices. This is an important contribution for decision makers to fulfil their need for environmental performance comparability with an adequate scheme
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