Integrating Life Cycle Assessment into the electric model Stella: A case for Germany.How to include the Planetary Boundaries concept

Electricity is an essential commodity for modern life, which is a driving force for social and economic development. However, electricity generation is not exempt from environmental impacts. In Germany, the energy sector still contributes 30 % to the national greenhouse gas emissions in 2020 (UBA 2021). Even though, the threat of global warming has prompted energy transition policies to ensure a secure, affordable and environmentally compatible electricity supply (BWMi 2019).The path to the energy transition is not unique. Energy system models (ESM) provide scenarios to assess alternatives. Yet, ESM focus on a techno-economic perspective and direct emissions. Therefore, frameworks that couple Life Cycle Assessment (LCA) and ESM have increased interest. Moreover, planetary boundaries (PB) in combination with LCA promise to assess sustainability. The PB concept incorporates an external reference to compare environmental alternatives, and external references are quantitative boundaries that describe the ecological limits of earth system processes. They define a desirable state in which Earth´s system must operate to sustain human development (Rockström, Steffen et al. 2009). This study assesses the sustainability of future electricity mixes based on the PB framework. The study presents Stella, an electricity model for European countries based on Calliope (Jesse, Morgenthaler et al. 2020). This multi-scale energy system modelling framework is python-based and open-source. Preliminary results suggest that wind power as the best compromise in terms of cost and environmental impacts. Fossil fuel technologies add to climate change and contribute considerably to toxic related categories and water eutrophication. From the perspective of PB, biomass is a high contributor to the biochemical flow of nitrogen. Initial results suggest paying attention to technologies that might interfere with the nitrogen cycle