a b s t r a c tThe German government has set itself the target of reducing the country's GHG emissions by between 80 and 95% by 2050 compared to 1990 levels. Alongside energy efficiency, renewable energy sources are set to play the main role in this transition. However, the large-scale deployment of renewable energies is expected to cause increased demand for critical mineral resources. The aim of this article is therefore to determine whether the transformation of the German energy system by 2050 ("Energiewende") may possibly be restricted by a lack of critical minerals, focusing primarily on the power sector (generating, transporting and storing electricity from renewable sources). For the relevant technologies, we create roadmaps describing a number of conceivable quantitative market developments in Germany. Estimating the current and future specific material demand of the options selected and projecting them along a range of long-term energy scenarios allows us to assess potential medium-or long-term mineral resource restrictions. The main conclusion we draw is that the shift towards an energy system based on renewable sources that is currently being pursued is principally compatible with the geological availability and supply of mineral resources. In fact, we identified certain sub-technologies as being critical with regard to potential supply risks, owing to dependencies on a small number of supplier countries and competing uses. These sub-technologies are certain wind power plants requiring neodymium and dysprosium, thin-film CIGS photovoltaic cells using indium and selenium, and largescale redox flow batteries using vanadium. However, non-critical alternatives to these technologies do indeed exist. The likelihood of supplies being restricted can be decreased further by cooperating even more closely with companies in the supplier countries and their governments, and by establishing greater resource efficiency and recyclability as key elements of technology development.

The concept Material Input per Service Unit (MIPS) was developed 20 years ago as a measure for the overall natural resource use of products and services. The material intensity analysis is used to calculate the material footprint of any economic activities in production and consumption. Environmental assessment has developed extensive databases for life cycle inventories, which can additionally be adopted for material intensity analysis. Based on practical experience in measuring material footprints on the micro level, this paper presents the current state of research and methodology development: it shows the international discussions on the importance of accounting methodologies to measure progress in resource efficiency. The MIPS approach is presented and its micro level application for assessing value chains, supporting business management, and operationalizing sustainability strategies is discussed. Linkages to output-oriented Life Cycle Assessment as well as to Material Flow Analysis (MFA) at the macro level are pointed out. Finally we come to the conclusion that the MIPS approach provides relevant OPEN ACCESS Resources 2014, 3 545 knowledge on resource and energy input at the micro level for fact-based decision-making in science, policy, business, and consumption.

Wuppertal Institut | 1 AbstractThe economic assessment of low-carbon energy options is the primary step towards the design of policy portfolios to foster the green energy economy. However, today these assessments often fall short of including important determinants of the overall cost-benefit balance of such options by not including indirect costs and benefits, even though these can be gamechanging. This is often due to the lack of adequate methodologies.The purpose of this paper is to provide a comprehensive account of the key methodological challenges to the assessment of the multiple impacts of energy options, and an initial menu of potential solutions to address these challenges.The paper first provides evidence for the importance of the multiple impacts of energy actions in the assessment of low-carbon options.The paper identifies a few key challenges to the evaluation of the co-impacts of low-carbon options and demonstrates that these are more complex for co-impacts than for the direct ones. Such challenges include several layers of additionality, high-context dependency, and accounting for distributional effects.The paper continues by identifying the key challenges to the aggregation of multiple impacts including the risks of overcounting while taking into account the multitude of interactions among the various co-impacts. The paper proposes an analytical framework that can help address these and frame a systematic assessment of the multiple impacts.

We use cluster analysis and material flow accounting to describe patterns of resource use in German households. Data on socio-demographic characteristics, and expenditures on fuel, electricity and household equipment allow for a differentiation of seven different household types. The corresponding resource use, expressed in Material Footprint per person and year, is calculated based on cradle-to-gate material flows of average household goods. Our results show that patterns of resource use are mainly driven by the use of fuel and electricity and the ownership of cars. The quantified Material Footprints correlate to higher social status and are also linked to city size, age and household size. Affluent, established and/or younger families living in rural areas typically show the highest amounts of durables and expenditures on non-durables, thus exhibiting the highest use of natural resources.