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Environmental analysis of enhanced geothermal systems through life-cycle assessment and induced seismicity risk criteria

Proceedings article published in 2012 by Isabelle Blanc, Martino Lacirignola
This paper was not found in any repository; the policy of its publisher is unknown or unclear.
This paper was not found in any repository; the policy of its publisher is unknown or unclear.

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Preprint: policy unknown
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Postprint: policy unknown
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Published version: policy unknown

Abstract

The development of geothermal systems based on enhanced low-temperature reservoirs is arousing attention as a promising alternative for electricity production using renewable energy. However, promoting the development of this technology is inappropriate without a critical assessment of its impacts on the environment. In fact despite the low emissions during the operation phase, large quantities of energy and materials are required for the construction of the plant. The investigation of the impacts of enhanced geothermal systems (EGS) from a cradle to grave perspective can be effectively performed through the life-cycle assessment (LCA) methodology with a relevant set of environmental criteria adapted to EGS. Such customized assessment is applied to the analysis of ten significant EGS design options in central Europe. A large variety of interdependent factors, related both to reservoir conditions and technical choices, determines the size of the installation and the final amount of electricity delivered to the grid. Hence, different sets of parameters are defined to identify the relevant scenarios, accounting the influence of the geothermal flow rate and its temperature, the number and the depth of the boreholes, the reinjection strategy, the power supply process at drilling stage and the risk of induced seismicity. The latter is a key factor that is progressively gaining importance at design stage, especially after the suspension of the project in Basel (Switzerland) and the experiences of current EGS installations. Hence seismicity risk has been identified as a fifth criteria, together with the four end points proposed by the method IMPACT2002+, to assess the environmental performances of EGS along a multi-criteria approach. Results show that impacts of EGS are comparable to those of other renewable energy technologies and significantly lower than those of conventional power plants. The comparison among the ten scenarios enables to formulate recommendations on the environmental suitability of their design. Finally, the risk of induced seismicity is highlighted as a key discriminating factor, as it increases inversely with the environmental benefit.