Hydrogen-powered aviation is promoted as a low-carbon alternative for future long-distance air travel, but its broader environmental impacts remain unclear. This study evaluates the potential environmental impacts of six future air travel pathways in Sweden, including e-kerosene, liquid hydrogen, and fossil kerosene, using prospective life cycle assessment. Results show that hydrogen-powered aviation has lower global warming potential than fossil kerosene but higher impacts on other environmental issues, such as toxicity and land use. Key hotspots include resources in energy infrastructure and energy use in fuel production and airport operations, however, resource substitutions and energy efficiency improvements have limits. This study highlights the potential environmental benefits and tradeoffs of hydrogen-powered aviation, and also the dependency of aviation on other sectors. Further research should integrate technological innovations in long-distance air travel pathways with scenarios that account for demand-side measures, as well as regulatory, political, and economic barriers. 

With the circular economy (CE) gaining more traction worldwide, local authorities are engaging in efforts to develop circular strategies at the urban level. Developing and monitoring such strategies require detailed quantitative information on material and energy flows, which can be obtained through an urban metabolism (UM) analysis. This study demonstrates a bottom-up approach to analyze UM at the sectoral level based on material and energy flow analysis (MEFA), aiming to examine its utility within the context of the CE. The analysis is performed for Umeå urban area (Sweden) with a 5-year timeframe (2017–2021). The application of MEFA provides a detailed quantitative description of material and energy flows per sector, indicating the critical sectors in terms of resource consumption and waste generation and the most significant flows. More specifically, it reveals that the construction sector and households are key sectors within Umeå’s UM and that construction materials, food products, fossil fuels, and drinking water are significant metabolic flows. Furthermore, the application of MEFA with a multi-year timeframe uncovers trends in consumption rates of materials and generation rates of waste and emissions, revealing, for example, the correlation of material consumption and waste generation with the level of construction activity. Overall, by illustrating the potential of MEFA to provide a detailed quantitative analysis of material and energy flows, this study emphasizes its utility in supporting the design and monitoring of circular strategies at the urban level. At the same time, it highlights limitations of the method and suggests areas for future research.

Purpose: This study aims to investigate how the coupling of Material and Energy Flow Analysis (MEFA) with Life Cycle Assessment (LCA) under an urban metabolism (UM) perspective (referred to as the UM-LCA approach) can support the design, evaluation, and monitoring of urban-level circular strategies. For this purpose, we apply the UM-LCA approach to the urban area of Umeå (Sweden) by expanding the goal and scope of a recent MEFA study conducted by the authors of the article.

Methods: The modeling combines MEFA with LCA and is performed both retrospectively and prospectively. The MEFA was performed in the prior study following a bottom-up approach to map and quantify material and energy flows in the urban system at the sectoral level. The quantified flows are used in the present study to construct the life cycle inventory (LCI) model of the urban system. The LCI model is first used as a basis of the retrospective LCA (rLCA), which is conducted to assess the environmental performance of the urban system with its sectors. The LCI model is then modified according to future scenarios and is used as a basis of the prospective LCA (pLCA), which is performed to assess the environmental implications of implementing circular strategies in the future.

Results and discussion: The rLCA shows that the construction and household sectors are major drivers of environmental impacts in the urban system, with households being the largest contributors to 11 out of 12 analyzed impact categories. It also reveals the most impacting flows within these sectors, including food in households and steel in the construction sector. These findings indicate that the construction and household sectors and their most impacting flows should be prioritized in a circular strategy. Furthermore, the pLCA highlights that a future circular strategy promoting reductions in the material used in these two sectors could lead to higher reductions in all impact categories, ranging from 4.3 to 8.6%, than a strategy focused only on recycling, which could lead to reductions ranging from 0.2 to 1.2%.

Conclusions: This study concludes that the UM-LCA approach has great potential to comprehensively analyze, both retrospectively and prospectively, the environmental performance of an urban system providing valuable insights that could support policy makers in designing, assessing, and monitoring urban-level circular strategies. However, further research should address identified limitations of the UM-LCA approach (e.g., limited available data, inability to consider social and economic aspects) to facilitate its applicability and enhance its comprehensiveness.

Global textile production and consumption has increased steadily over the past 15 years, which has caused significant impacts on the climate and the environment. In 2022, the EU launched a strategy for sustainable and circular textiles, stating that extending the life of textile products is the most efficient way to reduce their impact on the climate and the environment. Shell jackets for outdoor use are textile products that are frequently discarded by their first users and re-sold on the second-hand market. This study evaluates the performance of 16 second-hand shell jackets from three second-hand stores in Sweden via material testing of four key functional aspects. Comparing the results with the jackets’ original performance, this study describes the change in functionality over time. The results indicate that air permeability does not change significantly, whereas water repellency, water penetration resistance, and breathability decrease over time, although they do so at different rates. With the aim of promoting circularity and encouraging longer product use, this study also compares the price evolution of jackets with their functionality over time. The results reveal that the resale price of the jackets is lower than could be expected based on the level of remaining functionality in the jackets.

Food production and consumption significantly contribute to climate change. The public sector, which procures large quantities of food, has a crucial role in steering toward more sustainable food systems. More empirical studies involving practitioners are called for to understand the complexity of sustainable public food procurement. This study examines how actors interpret and implement sustainability in food procurement, as well as their influence on this process. A comprehensive analysis of multi-actor collaboration and stakeholder engagement involving interviews with key actors such as procurement officers, wholesalers, chefs, and food producers is presented. Findings highlight a consensus on the need for sustainability measures, such as purchasing local and organic products. The results showcase the potential transformation of power dynamics within the supply chain in response to modifications in procurement standards toward local produce and the overuse of product-specific criteria. However, assuming that local is invariably sustainable carries the risk of falling into the “local trap” when the consequence of procuring local varies and requires further investigation. The influence of system-level factors, including market dynamics and regulatory frameworks, plays a significant role in implementing sustainable procurement, as well as alignment and coordination in the supply chain.

Life cycle assessments of circular economy measures (CE LCA) of consumer products have been criticized for oversimplifying important aspects of the use phase such as user behavior and rebound effects, limiting our understanding of the environmental performance of circular economy measures. This study tests the usefulness of a framework designed to facilitate accounting for such aspects, by applying the framework to a case study of reuse of shell jackets enabled by “premium secondhand” outdoor stores. Methods for collecting use phase data were user surveys and interviews with store managers. Using the framework on this case study generated several novel insights which are interesting in themselves and as inputs to CE LCA. For instance, secondhand shell jackets have a significantly lower frequency of use during their first use span compared to the second and to shell jackets in the linear reference scenario. This implies that reuse in this case does not function as a mere use extension of otherwise similar use phases as is commonly assumed. The generation of such insights, which hitherto have been lacking in CE LCAs, points to the usefulness of the framework as a tool for opening the “black box” of the use phase in CE LCAs to improve understanding of the environmental performance of circular economy measures.

Aviation accounts for approximately five percent of global greenhouse gas emissions through the combustion of fossil fuels. This paper analyses the opportunities and challenges of mitigation measures in limiting travel volume, energy and emission intensity to reduce the climate impact of aviation in Sweden. Several measures are in place that aim to reduce the climate impact of the aviation industry, ranging from regulations to technology alternatives to fossil-based jet fuel. These measures face several crosscutting challenges, many of which are of a socio-economic and political nature, and these aspects are often neglected in favour of focusing on technological solutions. The market creation for alternatives to fossil-based jet fuel is a major challenge, as most consumers today have a limited awareness of and willingness to pay for these innovations. Policy measures in place are proven ineffective in incentivising change. An understanding of the industry as a socio-technical system is required. The value of this review is its broader consideration of the pathways to reduce aviation's climate impact, offering new perspectives and pointing to areas for further research considering all components, their interactions and interdependence.

Ambitious fossil-free targets imposed on the aviation industry worldwide demand a large volumetric supply of sustainable aviation fuel (SAF) to meet. Sweden's commitment to a 30% volume SAF blending target by 2030 attracts interest in local production. However, the sustainability of local production is largely unknown. Addressing this gap, we aim to explore potential SAF technology pathways and assess their environmental performances in Sweden. To do so, we utilize a socio-technical system (STS) approach for pathways selection and prospective life cycle assessment (LCA) for environmental impact assessment. As a result, we identify two lignocellulosic-based and two electrofuel-based pathways and evaluate their global warming potential, mineral depletion potential, ionizing radiation, land use, freshwater ecotoxicity and human toxicity impact in comparison to jet fuel. Our findings show that the well-to-wake global warming potential (100 years) of 30% SAF is on average 20% lower than that of jet fuel, with non-carbon dioxide species emitted in flight being the major contributors, prompting the need for urgent research efforts to mitigate their potential impacts. Under the assumption that no burdens are allocated to waste material used as feedstock, lignocellulosic-based 100% SAF has a well-to-pump climate impact (100 years) ranging from 0.6 to 1.5 g CO2−eq/MJ compared to jet fuel's 10.5 g CO2−eq/MJ. In contrast, the well-to-pump climate impact (100 years) of electrofuel-based 100% SAF (ranging from 7.8 to 8.2 g CO2−eq/MJ) is only marginally lower than that of jet fuel, mainly attributed to emissions from steel and concrete produced for wind turbine manufacturing. In general, the use of electricity generated by wind power could shift the potential environmental burden associated with jet fuel from global warming to mineral depletion, land use, freshwater ecotoxicity and human toxicity. The STS approach underscores the need to prioritize changes in systems underpinning SAF production, in turn supporting policy and investment decision making.

While it may be impossible to accurately predict what the world will look like in the future, we can be certain that it will be different from the world of today. By extension, we know that using today's data in life cycle assessment (LCA) studies claiming to represent future scenarios is problematic. For the future impact of products to be estimated in a consistent and meaningful manner in LCA, the background system, most commonly the ecoinvent database, needs to be projected into the future alongside the foreground system modeled in a given study. Futura is a new piece of open-source software which allows LCA practitioners to create and share novel background databases representing arbitrary scenarios. It allows users to import a base database and then start making targeted changes. These changes take three main forms—adding new technologies, regionalizing new or existing technologies, and altering market compositions. All changes made are automatically added to a "recipe." This recipe file can be shared publicly. This recipe can be imported by other users and used to exactly recreate the modified database. The additive and transparent nature of this system means that initially simple scenarios can be built upon by others to progress toward more comprehensive scenarios in a stepwise manner. The inability to build on the work of others is a serious barrier to the progress of the LCA field. Futura goes some way to reduce this barrier in the field of prospective LCA.