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.

The nutritional footprintIntegrated methodology using environmental and health indicators to indicate potential for absolute reduction of natural resource use in the field of food and nutrition Originally published in:Journal of Cleaner Production, 132 (2016), 161-170 DOI: 10.1016161-170 DOI: 10. /j.jclepro.2015 This is the author's version of a work that was accepted for publication. Changes resulting from the publishing process, such as editing, corrections and structural formatting, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in the Journal cited above. AbstractThe field of nutrition will face numerous challenges in coming decades; these arise from changing lifestyles and global consumption patterns accompanied by a high use of resources.Against this background, this paper presents a newly designed tool to decrease the effect on nutrition, the so-called Nutritional Footprint. The tool is based on implementing the concept of a sustainable diet in decision-making processes, and supporting a resource-light society.The concept integrates four indicators in each of the two nutrition-related fields of health and environment, and condenses them into an easily communicable result, which limits its results to one effect level. Applied to eight lunch meals, the methodology and its calculations procedures are presented in detail. The results underline the general scientific view of food products; animal-protein based meals are more relevant considering their health and environmental effects. The concept seems useful for consumers to evaluate their own choices, and companies to expand their internal data, their benchmarking processes, or their external communication performance. Methodological shortcomings and the interpretation of results are discussed, and the conclusion shows the tools' potential for shaping transition processes, and for the reduction of natural resource use by supporting food suppliers' and consumers' decisions and choice.

Resource efficiency potential of selected technologies, products and strategies Originally published as:Rohn, H. ; Pastewski, N. ; Lettenmeier, M. ; Wiesen, K. ; Bienge, K. (2014) AbstractDespite of rising prices for natural resources during the past 30 years, global consumption of natural resources is still growing. This leads to ecological, economical and social problems. So far, however, limited effort has been made to decrease the natural resource use of goods and services. While resource efficiency is already on the political agenda (EU and national resource strategies), there are still substantial knowledge gaps on the effectiveness of resource efficiency improvement strategies in different fields. In this context and within the project "Material Efficiency and Resource Conservation", the natural resource use of 22 technologies, products and strategies was calculated and their resource efficiency potential analysed.In a preliminary literature-and expert-based identification process, over 250 technologies, strategies, and products, which are regarded as resource efficient, were identified. Out of these, 22 subjects with high resource efficiency potential were selected. They cover a wide range of relevant technologies, products and strategies, such as energy supply and storage, Green IT, transportation, foodstuffs, agricultural engineering, design strategies, lightweight construction, as well as the concept "Using Instead of Owning". To assess the life-cycle-wide resource use of the selected subjects, the material footprint has been applied as a reliable indicator. In addition, sustainability criteria on a qualitative basis were considered.The results presented in this paper show significant resource efficiency potential for many technologies, products and strategies.

Background: Global targets for reducing resource use have been set by organizations such as the International Resource Panel and the European Commission. However, these targets exist only at the macro level, e.g., for individual countries. When conducting an environmental analysis at the micro level, resource use is often neglected as an indicator. No sum parameter indicating all abiotic and biotic raw materials has been considered for life cycle assessment, as yet. In fact, life cycle assessment databases even lack some of the specific input flows required to calculate all abiotic and biotic raw materials. In contrast, the cumulative energy demand, an input-based indicator assessing the use of energy resources, is commonly used, particularly when analyzing energy-intensive product systems. Methods: In view of this, we analyze the environmental relevance of the sum parameter abiotic and biotic raw material demand, which we call the material footprint. First, we show how abiotic and biotic raw material demand can be implemented in the Ecoinvent life cycle assessment database. Employing the adapted database, the material footprint is calculated for 12 individual datasets of chosen materials and crops. The results are compared to those of the cumulated energy demand and four selected impact categories: climate change, ozone depletion, acidification, and terrestrial eutrophication. Results: The material footprint is generally high in the case of extracted metals and other materials where extraction is associated with a large amount of overburden. This fact can lead to different conclusions being drawn compared to common impact categories or the cumulative energy demand. However, the results show that both the range between the impacts of the different materials and the trends can be similar. Conclusions: The material footprint is very easy to apply and calculate. It can be implemented in life cycle assessment databases with a few adaptions. Furthermore, an initial comparison with common impact indicators suggests that the material footprint can be used as an input-based indicator to evaluate the environmental burden, without the uncertainty associated with the assessment of emission-based impacts.