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The demand for many resources has increased significantly over the last decades due to their growing importance for industrial and technological development. Thus, various methods were developed to assess availability constraints of resources in relation to their vulnerability within countries and/or sectors (criticality). However, these methods display several shortcomings. Thus, the aim of the introduced approach is, to enhance the assessment of critical resource use on country level with the SCARCE method, by considering the two dimensions criticality (with the sub dimensions availability and vulnerability) and societal acceptance (with the sub dimensions compliance with social standards and compliance with environmental standards). For five of the 12 introduced categories measuring availability constraints the country specific import mix is used to determine availability constraints of resources individually for the country under consideration. These results can further be compared with global constraints (which are calculated based on global production data) to determine if the country under consideration performs worse or better than the global average. To measure social aspects the categories small scale mining, geopolitical risk and human rights abuse are introduced. Environmental aspects are considered within the categories sensitivity of the local biodiversity, climate change and water scarcity. Additionally, next to metals also fossil fuels are included allowing a direct comparison of both abiotic resources. The SCARCE method is applied for the case study of Germany for which criticality results are presented and their plausibility is validated. It is shown that for Germany tungsten is the raw material showing high risks in all considered dimensions excluding the sub dimension vulnerability. Its high availability constraints are defined by the categories political stability, primary material use and price fluctuations. Further, due to the countries tungsten is imported from (e.g. Bolivia), its compliance with social and environmental standards is low. To enhance the applicability of the SCARCE method, indicator results are provided for 40 resources to assess their availability constraints as well as their compliance with social and environmental standards.

In the last decade, several methods were developed to determine potential supply risks due to short term socio-economic aspects. One of them is the ESSENZ method (comprehensive method to measure and assess resource efficiency of products in the context of sustainable development) developed by the authors. Due to newly available data (e.g., production statistics) the characterization factors (CFs) of the ESSENZ method were updated (based on data from the years 2011 to 2015, with focus on 2014 and 2015) and compared with the original CFs (based on data from the years 2009 to 2013, with focus on 2012 and 2013) for six of the overall eleven categories. The goal of the paper is to analyze if changes in the underlying data are adequately reflected in the CFs of ESSENZ for the considered categories. Further, the updated CFs are provided. The six categories are analyzed by comparing original and updated CFs and clustering them into four groups: declining, emerging, persistent, and non-occurring potential supply risks. Significant differences in the CFs are evaluated by analyzing changes in the underlying data as well as the steps to determine the CFs. It could be shown, that for most of the considered categories and resources changes in the underlying data are reflected adequately in the CFs. However, some methodological challenges of ESSENZ, which limit the reflection of potential supply risks changes, could also be identified.

Purpose Ocean acidification due to the absorption of increasing amounts of atmospheric carbon dioxide has become a severe problem in the recent years as more and more marine species are influenced by the decreasing pH value as well as by the reduced carbonate ion concentration. So far, no characterization model exists for ocean acidification. This paper aims to establish such a characterization model to allow for the necessary future inclusion of ocean acidification in life cycle assessment (LCA) case studies. Methods Based on a cause-effect chain for ocean acidification, the substances carbon monoxide, carbon dioxide, and methane were identified as relevant for this impact category. In a next step, the fate factor representing the substances' share absorbed by the ocean due to conversion, distribution, and dissolution is determined. Then, the fate sensitivity factor is established reflecting the changes in the marine environment due to the amount of released hydrogen ions per gram of substance (category indicator). Finally, fate and fate sensitivity factors of each substance are multiplied and set in relation to the reference substance, carbon dioxide, thereby delivering the respective characterization factors (in kg CO 2 eq) at midpoint level.Results and discussion Characterization factors are provided for carbon monoxide (0.87 kg CO 2 eq), carbon dioxide (1 kg CO 2 eq), and methane (0.84 kg CO 2 eq), which allow conversion of inventory results of these substances into category indicator results for ocean acidification. Inventory data of these substances is available in common LCA databases and software. Hence, the developed method is directly applicable. In a subsequent contribution analysis, the relative contribution of the three selected substances, along with other known acidifying substances, to the ocean acidification potential of 100 different materials was studied. The contribution analysis confirmed carbon dioxide as the predominant substance responsible for more than 97 % of the total ocean acidification potential. However, the influence of other acidifying substances, e.g., sulfur dioxide, should not be neglected. Conclusions Evaluation of substances contributing to ocean acidification is of growing importance since the acidity of oceans has been increasing steadily over the last decades. The introduced approach can be applied to evaluate product system related impacts of ocean acidification and include those into current LCA practice.

Availability of abiotic resources has been a topic of concern in recent years, resulting in several approaches being published to determine their availability on country and product level. However, the availability of biotic materials has not been analyzed to this extent yet. Therefore, an approach to determine possible limitations to availability of terrestrial biotic materials over the entire supply chain is introduced. The approach considers 24 categories overall as well as associated category indicators for the five dimensions: physical, socio-economic, abiotic, social and environmental constraints. This ensures a comprehensive availability assessment of bio-based product systems. The approach is applied to a case study comparing biodiesel produced from rapeseed and soy beans. The study shows that the determination of indicator values is feasible for most categories and their interpretation leads to meaningful conclusions. Thus, the approach leads to a more comprehensive assessment of availability aspects and supports better informed decision making in industry and policy.