Hydrogen (H2) fuels are seen as alternative propulsion fuels to reduce aviation’s contribution to climate change as it does not produce carbon dioxide upon combustion. One major challenge for this transition is that hydrogen production routes often entail emissions that drastically reduce the environmental benefits of adopting the technology. Low-impact H2 production is associated with three processes; electrolysis powered by renewable energy, biological fermentation and biomass gasification. Impacts of the latter two can potentially be further reduced by carbon capture and storage. Several datasets to support life cycle assessments (LCAs) of mentioned H2 production routes exist, but are limited by different temporal and geographical scopes. Future changes in energy systems as well as technology developments will have a major effect on the long-term impacts of hydrogen production. Not considering these changes will distort decision-making based on prospective assessments. This study addresses this gap by harmonizing existing data for the three most prominent water electrolysis technologies and developing prospective H2 production life cycle inventory datasets for Europe. Only the production of hydrogen itself is considered, excluding liquefaction, storage and distribution to the aircraft refueling point. We consider the technological changes that are partially expected to lead to dramatic reductions in material intensities of the electrolysers. By harmonizing regionally specific background data, this work contributes to a clearer understanding of the conditions under which green H2 fuels can deliver substantial climate benefits as future aviation fuels.

Environmentally extended multi-regional input–output (EEMRIO) analysis provides a robust methodology for assessing economic, social, and environmental footprints across nations and regions. Increasing its geographical resolution is essential for addressing local environmental issues and informing targeted policy decisions. While subnational EEMRIOs ideally rely on survey data, such data are often unavailable or resource-intensive to process. As a result, partitioners resort to proxies and algorithms. Yet, the transparency of these algorithms and the underlying data are often suboptimal. Here, we present a novel, open-source, top-down regionalization approach applicable to any EEMRIO database. Our method builds on location quotients (LQ), extending their application to a multi-regional framework. This extension ensures calculations remain traceable, eliminates the need for supplemental balancing procedures, and requires minimal, readily available additional proxy data, making it highly accessible for practitioners. Using European steel trade as a proof-of-concept, we demonstrate how this approach assesses local impacts, highlights local–global trade interactions, and identifies opportunities that national IO data often obscure.

Recent research has emphasized the need to adapt life cycle inventories and life cycle impact assessments to account for changes in future scenarios. This is mostly achieved by using Integrated Assessment Models (IAMs), which combine environmental and economic data to develop prospective life cycle inventories (LCIs). However, running complex IAMs to simulate scenarios is computationally expensive, and the resulting data is not always aligned with the geographical scope of background inventories. This study explores the potential of machine learning (ML) to create prospective water-scarcity characterisation factors by forecasting the AWARE factor for ~ 9700 watersheds globally. Historical time series of water-scarcity characterisation factors are generated using the global freshwater model WaterGAP v2.2d and the AWARE method. Several ML models are trained on these historical datasets and benchmarked using symmetric mean absolute percentage error (sMAPE). The best-performing model, N-Beats, is then used to forecast AWARE values through 2032. The results demonstrate that ML can produce spatially and temporally explicit forecasts with reasonable accuracy (median sMAPE ~ 28%). However, the models primarily capture seasonal patterns rather than long-term structural trends and the results are sensitive to the quality and representativeness of the training data. This study highlights both the potential and the limitations of time series forecasting for developing prospective characterisation factors in life cycle assessment.

Widespread adoption of electric vehicles poses challenges due to critical raw material (CRM) requirements. The European Union (EU) is now dependent on other countries for supply of these materials, but wants to increase self-sufficiency for primary extraction to 10 % in 2030. Here we map and quantify Europe's raw material reserves and resources, revealing promising deposits for most minerals. Our analysis indicates that, assuming a high development scenario, for lithium, nickel and copper the planned extraction in Europe is sufficient to meet at least 10 % ofdemand for E-mobility in 2030, as the EU's proposed target dictates. The projected extraction of cobalt, natural graphite and REE, will probably not reach 10 % of the demand in 2030. For REE there is no European production projected. To meet these targets and increase the EU's self-sufficiency, CRM extraction in Europe needs to increase, in parallel with implementing circular economy efforts to reduce material demand.

Diversifying supply chains through reshoring and friendshoring is increasingly proposed as a key strategy for supply security and resilience. Quantitative analyses characterizing to what extend diversification shield countries from supply disruptions remain however scarce. In this paper, we present a methodology to assess the supply risk exposure of countries in different supply diversification scenarios – business-as-usual, reshoring, friendshoring. For each scenario, the propagation of three types of upstream disruptions – supply shortage, export restriction, bilateral trade conflict – is simulated. A fragility ratio metric is introduced to quantify the potential downstream shortages caused by these disruptions. A novel friendshoring modelling approach is also proposed. It consists in determining risk-optimized trade relations based on criteria such as supply concentration and UN voting similarity. The Python-based model is tested on the case of diversified photovoltaics supply chains, e.g., if the US, EU, and India increase domestic production from polysilicon to module. Beyond building up manufacturing capacities, choosing between vertical integration and trade is highly determinant in risk exposure. Each diversification scenario shows pros and cons depending on the country and process considered. Overall, this paper underlines the need for supply risk research to nuance diversification recommendations. It would be particularly helpful to improve indicators accounting for a region's technical and economic ability to supply a given product, and to realistically model the challenges of reshoring.

The supply of critical raw materials, especially titanium, poses a significant challenge for the aviation sector. Increased circularity is often proposed as a solution by industry and policymakers. However, the effects of circular strategies remain insufficiently understood. Therefore, this paper analyses different circular strategies, namely recycling, a pure lifetime extension, and an enhanced lifetime extension that includes an engine aircraft, based on real-world data up to the year 2040. The findings indicate that recycling retired aircraft only marginally affects the required rising inflow of titanium by less than 5%. The engine upgrade strategy shows similar results. In contrast, a pure lifetime extension shows the greatest potential for mitigating supply constraints and can be further enhanced to a potential of more than 10% when combined with recycling. The results highlight the complexity of circular strategies and emphasise a stronger focus on lifetime extension for the aviation sector and other industrial sectors.

With initiatives such as the European Green Deal establishing more stringent environmental requirements, there is an increasing need to develop aircraft technologies and sustainable aviation practices with reduced climate impacts. Additionally, conventional environmental Life Cycle Assessments (LCAs) often struggle to capture the dynamic and complex nature of aircraft operations; in particular, non-CO₂ in-flight impacts, which contribute significantly to climate change, are often overlooked. In this study, we improve a discrete-event LCA approach with a climate impact evaluation model and apply it to scenario analyses comparing different aircraft designs, fuel types, and flight schedules. Our findings reveal that, contrary to previous LCA studies, the climate impact per kilometre flown increases with longer flight distances and that an efficiently planned flight schedule can reduce the overall environmental impact. The study highlights the necessity of incorporating non-CO₂ effects and operational scenarios into LCA to achieve a more accurate understanding of aviation's environmental impact.

Silicon carbide (SiC) is a niche nonmetallic material that is essential in many industrial processes. Here, we integrate material flow analysis and supply chain resilience analysis to understand global SiC stocks and flows and to assess its supply chain. We use industry interviews to fill data gaps and collect information on the SiC system to overcome data scarcity. We find that globally around 1000 kt of SiC is produced each year. The biggest use of SiC is the abrasives industry (40%), followed by metallurgy (28%), refractories (20%), technical ceramics (0.7%), other uses (0.7%), and semiconductors (0.01%). As an energy-intensive material, the SiC supply chain is under pressure, increasing the relevance of resilience considerations. Besides typical supply chain risks such as low diversity of supply and geopolitical trade restrictions, SiC particularly faces risks due to its energy-intensive production process and associated emissions. In the SiC semiconductor supply chain, losses of nearly 75% are a particular issue. Due to high demand in the SiC market, stockpiles are negligible, and substitution is difficult in most sectors. We find that in the case of SiC, sustainability measures such as use reduction, recycling, or decreasing energy use or emissions would also positively contribute to supply chain resilience. This article met the requirements for a gold-gold JIE data openness badge described at http://jie.click/badges.

Bio-based polymers may present a sustainable, circular way to reduce the environmental impact of plastics because they are produced from biomass that absorbs CO₂ during its growth. However, sourcing (type of biomass used and cultivation location), production, and end-of-life affect the environmental impact of bio-based plastics. We assessed the effect of sourcing and end-of-life options on the environmental impact of bio-based high-density polyethylene (bio-HDPE) in 31 sourcing scenarios and five end-of-life options. Our study found that careful consideration of biomass sourcing (biomass type and production location) and end-of-life is needed to optimize the environmental impact of bio-based plastics. If these aspects are not considered, the environmental impact of bio-HDPE may exceed that of its petrochemical-based counterpart. The direct availability of fermentable sugars indicated a lower environmental impact. The production location affected the resources needed for biomass cultivation and the environmental impact of processing due to the energy mix. Recently published guidelines do not allow biogenic carbon to be accounted for during the production stage, but only upon the incineration of the plastic. Our results show that this way of attributing biogenic carbon results in an apparent disadvantage for bio-based plastics compared to petrochemical-based plastics. Furthermore, it disadvantaged mechanical recycling of bio-based plastics compared to incineration, a result out of line with circular economy principles.

The anticipated increase in urban population of 2.5 billion people by 2050 poses significant environmental challenges. While the various environmental impacts of urbanisation have been studied individually, integrated approaches are rare. This study introduces a spatially explicit model to assess urbanization’s effects on ecosystem services (green infrastructure availability, cooling, stormwater retention) and the environmental impact of building construction (material demand, greenhouse gas emissions, land use). Applied to the Netherlands from 2018 to 2050, our results show that integrating green infrastructure development with building construction could increase green areas by up to 5% and stabilize or increase ecosystem service provisioning. Dense building construction with green infrastructure development is generally more beneficial across the Netherlands, reducing resource use and enhancing ecosystem services. Conversely, sparse construction with green infrastructure is more advantageous for newly built areas. These findings offer insights into the environmental consequences of urbanization, guiding sustainable urban planning practices.

Tin is an important metal for society with a high risk of supply disruptions. It is, therefore, classified as a critical material in many parts of the world. An exception is the European Union, for which tin was classified as a non-critical material in 2023. However, there are many discrepancies in the literature regarding the definitions and values of the indicators used to determine tin criticality in general, and recycling indicators in particular. Values for end-of-life recycling rate (EoL RR) range between 20% and 75%, and values for end-of-life recycling input rate (EoL RIR) range between 11% and 32%. In this paper, we critically assess the circularity and criticality indicator values for tin and calculate new values using material flow analysis. The new values for tin recycling indicators are lower than those used in most previous research, with a global EoL RR of 16% and an EoL RIR of 11% in 2017. Based on the updated recycling values, combined with a highly concentrated supply, high import reliance, and difficult substitution, we argue that the European Union should classify tin as a critical material. This reclassification can lead to more policy attention for tin, which can help reduce the impact of future supply disruptions and increase the resilience of the European and global tin supply chains.

As the aviation industry strives to minimise its environmental footprint, understanding the full life cycle impacts, including maintenance, becomes essential for sustainable development. This paper addresses the critical research gap in the environmental assessment of aircraft maintenance by conducting a comprehensive life cycle assessment based on an Airbus A320 aircraft. By combining a top-down check-level analysis and a detailed examination of the aircraft manufacturer's maintenance planning document, this study provides significant insights into the environmental implications of maintenance activities. The check-level analysis provides a general overview, while the analysis of the maintenance planning document delves into individual tasks, enabling the identification of components with the highest ecological impacts. This research emphasises the importance of including aircraft maintenance activities in life cycle assessment studies and provides valuable guidance for researchers, industry practitioners, and policy makers in prioritising sustainability measures and enhancing the environmental performance of aircraft throughout their life cycle.

Rare earth elements (REEs) are vital to the development of low-carbon technologies. There are rising concerns in the United States and elsewhere about REE supply chain stability and risks given the unvalidated perception in the heavy reliance of China, by far the largest REE supplier. However, the relationship between key countries at different stages of global REE supply chains remains unclear. Here, we use a dynamic flow analysis to explore supply dependence between the United States and China by tracing REE flows from mineral mining to market between 2000 and 2022. Our results indicate complementary and cooperative US–China interactions, especially after 2018 when the United States became a net exporter of REE and China's largest supplier, and China became the largest importer of the US REEs and manufacturer of REE-enabled low-carbon technologies. This intensifying interdependence stabilizes REE supply chains and highlights the importance of cooperative REE trade networks.

Each year, consumers return billions of new products to retailers. Despite growing concern over product destruction, post-return product flows are not well understood, and the full lifecycle environmental impacts of returns remain largely unknown. Building on a unique dataset covering over 630k returned apparel items in the EU, we map the flow of returned products under sustainable and conventional management practices, and quantify the full lifecycle impacts associated with returns using two illustrative apparel case studies. We find that 22%-44% of returned products never reach another consumer. Moreover, the GHG emissions associated with the production and distribution of unused returns can be 2–16 times higher than all post-return transport, packaging, and processing emissions combined. Our findings suggest that the environmental impacts eCommerce and specifically online apparel, may be systematically underestimated when returns are not accounted for, and highlight the urgent need to promote circular management practices that maximize use of returned products.