Open Access

The German Energiewende is a deliberate transformation of an established industrial economy towards a nearly CO2-free energy system accompanied by a phase out of nuclear energy. Its governance requires knowledge on how to steer the transition from the existing status quo to the target situation (transformation knowledge). The energy system is, however, a complex socio-technical system whose dynamics are influenced by behavioural and institutional aspects, which are badly represented by the dominant techno-economic scenario studies. In this paper, we therefore investigate and identify characteristics of model studies that make agent-based modelling supportive for the generation of transformation knowledge for the Energiewende. This is done by reflecting on the experiences gained from four different applications of agent-based models. In particular, we analyse whether the studies have improved our understanding of policies' impacts on the energy system, whether the knowledge derived is useful for practitioners, how valid understanding derived by the studies is, and whether the insights can be used beyond the initial case-studies. We conclude that agent-based modelling has a high potential to generate transformation knowledge, but that the design of projects in which the models are developed and used is of major importance to reap this potential. Well-informed and goal-oriented stakeholder involvement and a strong collaboration between data collection and model development are crucial.

The earth's capacity to absorb greenhouse gases is ultimately a critical limiting factor in the handling of metals. The fact that the demand for metals far exceeds their secondary production is extremely problematic at this point. Nevertheless, metals are crucial for climate protection and energy system transformation. Examples are the rare earth metal neodymium used in high-performance permanent magnets in wind turbines, the alkali metal lithium as the most important component in batteries, or the metal tellurium used in thin-film solar cells to generate solar power. It is therefore essential to promote the aspects of resource efficiency and to strengthen the critical role of metals in national and European policy programs. Next to a global solution, a European solo effort with predominantly market-based instruments and the effects of committed behaviour by civil society in the European Union (EU), show that the EU can make a considerable contribution to sustainable development on its own. Thus, a comprehensive approach is needed for sustainable metal management in the sense of a circular economy on the European level fostering sustainable production and consumption pathways. But, this need and the special role of metals are not seen in the current debate about resources in society and politics. Due to the fact that in public perception, metallic raw materials are often discussed as less urgent than energy or polymer raw materials, this article aims to highlight the critical role of metals. Further, the objective of this contribution is to show which prerequisites exist for the development and establishment of a holistic metal management and where political strategies have to start. Challenges needed to be overcome to achieve such a holistic metal strategy and management are highlighted. In particular, the role of the metal industry, circular product design and labelling and corresponding indicator systems is examined. In addition, the special role of digitalisation is being worked out. Finally, conclusions are drawn and shown which aspects have to be considered for a holistic metal strategy and management.

Water and energy are two pivotal areas for future sustainable development, with complex linkages existing between the two sectors. These linkages require special attention in the context of the energy transition. Against this background, this paper analyses the role of water availability in the development of solar thermal and photovoltaic power plants for the case of the Draa Valley in southern Morocco. Located in a semi-arid to arid mountainous area, the Drâa Valley faces high water stress - a situation expected to worsen due to climate change. At the same time, the region has one of the greatest potentials for solar energy in the world. To examine whether limited water availability could accelerate or delay the implementation of solar thermal and photovoltaic power plants, this paper compares regional water availability and demand in the Draa Valley for different scenarios, paying particular attention to potential socio-economic development pathways. The Water Evaluation and Planning System software is applied to allocate the water resources in the study region. The water supply is modelled under the Representative Concentration Pathway 8.5 climate scenario, while the water demand for the Drâa Valley is modelled for a combination of three socio-economic and two energy scenarios. The climate scenario describes a significant decrease in water availability by 2050, while the socio-economic and energy scenarios show an increase in water demand. The results demonstrate that during a sequence of dry years the reservoirs water availability is reduced and shortages in water supply can result in high levels of unmet demand. If this situation occurs, oasis farming, water for drinking and energy production could compete directly with each other for water resources. The energy scenarios indicate that the use of dry cooling technologies in concentrated solar power and photovoltaic hybrid systems could be one option for reducing competition for the scarce water resources in the region. However, given that energy generation accounts for only a small share of the regional water demand, the results also suggest that socio-economic demand reduction, especially in the agricultural sector, for example by reducing the cultivated area, will most likely become necessary.

Recent research on the natural resource use of private consumption suggests a sustainable Material Footprint of 8 tons per capita by 2050 in industrialised countries. We analyse the Material Footprint in Germany from 2015 to 2020 in order to test whether the Material Footprint decreases accordingly. We studied the Material Footprint of 113,559 users of an online footprint calculator and predicted the Material Footprint by seasonally decomposed autoregressive (STL-ARIMA) and exponential smoothing (STL-ETS) algorithms. We find a relatively stable Material Footprint for private consumption. The overall Material Footprint decreased by 0.4% per year between 2015 and 2020 on average. The predictions do not suggest that the Material Footprint of private consumption follows the reduction path of 3.3% per year that will lead to the sustainable consumption of natural resource

The waste prevention program (WPP) from 2013 must be evaluated every 6 years and updated if necessary. The review and evaluation of the implementation of the WPP took place within the scope of the project. Based on the analysis results for the implementation of the WPP at federal, state and municipal level and an assessment of existing prevention potentials, concrete proposals for a possible further development and updating of the program on prioritized waste streams and corresponding priority prevention approaches were developed. In addition, structural adjustment and change needs of the WPP were worked out and further research was shown.