Reducing greenhouse gas (GHG) emissions in the transport sector is one of the biggest challenges in the German energy transition. Furthermore, sustainable development does not stop with reducing GHG emissions. Other environmental, social and economic aspects should not be neglected. Thus, here a comprehensive sustainability assessment for passenger vehicles is conducted for 2020 and 2050. The discussed options are an internal combustion engine vehicle (ICEV) fuelled with synthetic biofuel and fossil gasoline, a battery electric vehicle (BEV) with electricity from wind power and electricity mix Germany and a fuel cell electric vehicle (FCEV) with hydrogen from wind power. The life cycle-based assessment entails 13 environmental indicators, one economic and one social indicator. For integrated consideration of the different indicators, the MCDA method Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is chosen. For the assessment, a consistent assessment framework, i.e. background scenario and system boundaries, and a detailed modelling of vehicle production, fuel supply and vehicle use are the cornerstones. The BEV with wind power is the most sustainable option in 2020 as well as in 2050. While in 2020, the second rank is taken by the ICEV with synthetic biofuel from straw and the last rank by the FCEV, in 2050 the FCEV is the runner-up. With the help of MCDA, transparent and structured guidance for decision makers in terms of sustainability assessment of motorized transport options is provided. Graphical abstract

Background: A further increase in renewable energy supply is needed to substitute fossil fuels and combat climate change. Each energy source and respective technologies have specific techno-economic and environmental characteristics as well as social implications. This paper presents a comprehensive approach for prospective sustainability assessment of energy technologies developed within the Helmholtz Initiative “Energy System 2050” (ES2050).Methods: The “ES2050 approach” comprises environmental, economic, and social assessment. It includes established life cycle based economic and environmental indicators, and social indicators derived from a normative concept of sustainable development. The elaborated social indicators, i.e. patent growth rate, acceptance, and domestic value added, address three different socio-technical areas, i.e. innovation (patents), public perception (acceptance), and public welfare (value added).Results: The implementation of the “ES2050 approach” is presented exemplarily and different sustainability indicators and respective results are discussed based on three emerging technologies and corresponding case studies: (1) synthetic biofuels for mobility; (2) hydrogen from wind power for mobility; and (3) batteries for stationary energy storage. For synthetic biofuel, the environmental advantages over fossil gasoline are most apparent for the impact categories Climate Change and Ionizing Radiation—human health. Domestic value added accounts for 66% for synthetic biofuel compared to 13% for fossil gasoline. All hydrogen supply options can be considered to become near to economic competitiveness with fossil fuels in the long term. Survey participants regard Explosion Hazard as the most pressing concern about hydrogen fuel stations. For Li-ion batteries, the results for patent growth rate indicate that they enter their maturity phase.Conclusions: The “ES2050 approach” enables a consistent prospective sustainability assessment of (emerging) energy technologies, supporting technology developers, decision-makers in politics, industry, and society with knowledge for further evaluation, steering, and governance. The approach presented is considered rather a starting point than a blueprint for the comprehensive assessment of renewable energy technologies though, especially for the suggested social indicators, their significance and their embedding in context scenarios for prospective assessments.

In order to analyse long-term transformation pathways, energy system models generally focus on economical and technical characteristics. However, these models usually do not consider sustainability aspects such as environmental impacts. In contrast, life cycle assessment enables an extensive estimate of those impacts. Due to these complementary characteristics, the combination of energy system models and life cycle assessment thus allows comprehensive environmental sustainability assessments of technically and economically feasible energy system transformation pathways. We introduce FRITS, a FRamework for the assessment of environmental Impacts of Transformation Scenarios. FRITS links bottom-up energy system models with life cycle impact assessment indicators and quantifies the environmental impacts of transformation strategies of the entire energy system (power, heat, transport) over the transition period. We apply the framework to conduct an environmental assessment of multi-sectoral energy scenarios for Germany. Here, a ‘Target’ scenario reaching 80% reduction of energy-related direct CO₂ emissions is compared with a ‘Reference’ scenario describing a less ambitious transformation pathway. The results show that compared to 2015 and the ‘Reference’ scenario, the ‘Target’ scenario performs better for most life cycle impact assessment indicators. However, the impacts of resource consumption and land use increase for the ‘Target’ scenario. These impacts are mainly caused by road passenger transport and biomass conversion.