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The climate impacts of deep enhanced geothermal systems (EGS) have been understudied in the academic literature. Using life-cycle analysis (LCA) conducted in accordance with ISO 14040 and ISO 14044 standards, this paper explores the climate change impacts of two deep EGS. The first study was in Reykjanes, Iceland, where a single well, IDDP-2/DEEPEGS, was drilled to a depth of 4.6 km for the purposes of additional electricity production from an existing power plant. The second study involved two wells with side-tracks (depth > 5000 m), drilled to serve a new heat and power co-generation plant located on an old oil field site in Vendenheim, France. Climate change impacts for the sites were estimated in the range 1.6–17.4 gCO2e/kWh and 6.9–13.9 gCO2e/kWh for Reykjanes and Vendenheim, respectively. Although the EGS projects are very different, both outcomes are low when compared to non-renewable alternatives and akin to best-in-class renewable alternatives. The main impact at the Reykjanes demonstration site were the greenhouse gas emissions released from the borehole, an effect that could be avoided by carbon capture and storage/mineralisation/utilisation. In the case of Vendenheim, further reductions in emissions could be achieved via more extensive adoption of circular economy principles in design and procurement.

Pre-print / Óritrýnt handrit © 2022 Elsevier Ltd. All rights reserved., Environmental life cycle costing (ELCC) is a tool which aggregates five categories of monetary costs across a project's life cycle: investment, operation, maintenance, end-of-life, and externalities. This paper summarises the results from the first two ELCC studies involving deep enhanced geothermal systems (EGS). The ReCiPe method was used to transform life cycle impact factors into economic costs for externalities. The two case studies are the pilot EGS project in Reykjanes, Iceland and the Vendenheim co-generation plant in France. The ELCC of the Reykjanes project is estimated in the range 14.47–15.78 million euros, with investment and well drilling projected to constitute 83% of these amounts. An ELCC in the range 91.90–113.97 million euros is estimated for Vendenheim, with the production plant, well drilling, and operations and maintenance costs accounting for the majority. The levelized costs of energy associated with Vendenheim (mean Є45.0/MWh/year) and Reykjanes (mean Є16.5/MWh/year) are at the lower end of the range normally reported for geothermal power projects. Although the case studies cannot be directly compared since Reykjanes involves the drilling of a single well and Vendenheim a co-generation plant and two wells, the outcomes suggest that deep EGS projects may involve cost-savings compared to conventional geothermal power ventures.