Contribution to Ecoscienza 6/2014.   Challenge The German Federal Government’s energy concept ascribes renewable energies the role of an “important pillar of future energy supply”. According to its targets, renewable energies are to account for 18% of gross final energy consumption by 2020, rising to 60% by 2050. If only electricity generation is considered, the proportion of gross electricity consumption contributed by electricity from renewable energy sources is to increase to 80% by 2050. However, it is not only energy supply or climate protection criteria that play a crucial role in realising the Energiewende and, in particular, the development of renewable energy sources. A comprehensive sustainability assessment of the individual technologies must be made takin...