The deep underground promises attractive solutions for urgent societal challenges in energy production and CO2 reduction. In this talk, I will first part revisit past and ongoing GeoEnergy projects in Switzerland and abroad, focusing on Enhanced Geothermal Systems (EGS: Basel, Haute Sorne, Utah FORGE). Lessons learned from deep underground laboratories in Mont Terri, Grimsel, and Bedretto also offer important insights into the challenge of creating sustainable underground heat exchangers without damaging induced seismicity. However, public acceptance of EGS projects remains a significant challenge.

The Swiss Net Zero strategy demands that from 2050 onwards, several millions of tons of CO2 captured from waste incinerators, bio-gas plants, and cement factories will need to be sequestered. While offshore storage in saline aquifers or depleted oil and gas fields beneath the North Sea may be the option of choice, sequestration in saline aquiver in the Molasse basing might be economically, ecologically, and ethically the preferred choice. However, we currently do not know if storage is technologically feasible, safe, and societally acceptable, and to clarify the potential and risks, Pilot and Demonstration projects are urgently needed. In the second part of the presentation, I will describe the CITru injection test project considered by swisstopo and ETH, exploiting opportunistically an existing NAGRA borehole in Trüllikon. A volume of between 5,000 and 30,000 tons of biogenic CO2 may be injected from 2025 onwards if the ongoing feasibility study is successful, if funding can be secured, and if permits can be obtained.