Summary The present work aims to identify critical materials in water electrolysers with potential future supply constraints. The expected rise in demand for green hydrogen as well as the respective implications on material availability are assessed by conducting a case study for Germany. Furthermore, the recycling of end‐of‐life (EoL) electrolysers is evaluated concerning its potential in ensuring the sustainable supply of the considered materials. As critical materials bear the risk of raising production costs of electrolysers substantially, this article examines the readiness of this technology for industrialisation from a material perspective. Except for titanium, the indicators for each assessed material are scored with a moderate to high (platinum) or mostly high (iridium, scandium and yttrium) supply risk. Hence, the availability of these materials bears the risk of hampering the scale‐up of electrolysis capacity. Although conventional recycling pathways for platinum, iridium and titanium already exist, secondary material from EoL electrolysers will not reduce the dependence on primary resources significantly within the period under consideration—from 2020 until 2050. Notably, the materials identified as critical are used in PEM and high temperature electrolysis, whereas materials in alkaline electrolysis are not exposed to significant supply risks.

Households are either directly or indirectly responsible for the highest share of global anthropogenic greenhouse gas emissions. Hence, programs helping to improve human consumption habits have been identified as a comparatively cost-effective way to reduce household emissions significantly. Recently, various studies have determined strong regional differences in household carbon footprints, yet a case study for Germany has not been conducted. Local information and policies directed at household consumption in Germany thus devoid of any foundation. In this paper, we analyze the impact of different criteria such as location, income and size on household carbon footprints in Germany and demonstrate how the impact of GHG mitigation opportunities varies for different population segments. We use a multi-region input output hybrid LCA approach to developing a regionalized household carbon footprint calculator for Germany that considers 16 sub-national regions, 15 different household sizes, and eight different income and age categories. The model reveals substantial regional differences in magnitude and composition of household carbon footprints, essentially influenced by two criteria: income and size. The highest income household is found to emit 4.25 times as much CO 2 e than the lowest. We identify indirect emissions from consumption as the largest share of household carbon footprints, although this is subject to fluctuation based on household type. Due primarily to local differences in vehicle availability, income and nutrition, an average household in Baden-Wuerttemberg is found to have 25 % higher carbon footprint than its R. Miehe (&) Sustainable Production and Quality Management, Fraunhofer Institute for Manufacturing Engineering and Automation (IPA),

Till 2020 the predominant key success factors of battery development have been overwhelmingly energy density, power density, lifetime, safety, and costs per kWh. That is why there is a high expectation on energy storage systems such as lithium-air (Li-O2) and lithium-sulfur (Li-S) systems, especially for mobile applications. These systems have high theoretical specific energy densities compared to conventional Li-ion systems. If the challenges such as practical implementation, low energy efficiency, and cycle life are handled, these systems could provide an interesting energy source for EVs. However, various raw materials are increasingly under critical discussion. Though only 3 wt% of metallic lithium is present in a modern Li-ion cell, absolute high amounts of lithium demand will rise due to the fast-growing market for traction and stationary batteries. Moreover, many lithium sources are not available without compromising environmental aspects. Therefore, there is a growing focus on alternative technologies such as Na-ion and Zn-ion batteries. On a view of Na-ion batteries, especially the combination with carbons derived from food waste as negative electrodes may generate a promising overall cost structure, though energy densities are not as favorable as for Li-ion batteries. Within the scope of this work, the future potential of sodium-based batteries will be discussed in view of sustainability and abundance vs. maximization of electric performance. The major directions of cathode materials development are reviewed and the tendency towards designing high-performance systems is discussed. This paper provides an outlook on the potential of sodium-based batteries in the future battery market of mobile and stationary applications.

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