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As fossil fuels are phased out in favour of renewable energy, electric cars and other low-carbon technologies, the future clean energy system is likely to require less overall mining than the current fossil-fuelled system. However, material extraction and waste flows, new infrastructure development, land-use change, and the provision of new types of goods and services associated with decarbonization will produce social and environmental pressures at localized to regional scales. Demand-side solutions can achieve the important outcome of reducing both the scale of the climate challenge and material resource requirements. Interdisciplinary systems modelling and analysis are needed to identify opportunities and trade-offs for demand-led mitigation strategies that explicitly consider planetary boundaries associated with Earth’s material resources.

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The circular economy (CE) is a concept for sustainable resource management that aims to decrease environmental pressures that human activities put on the planet. First introduced in the 1960s, it recently gained popularity as positive, forward-looking narrative. In times of looming climate change, CE offers a ‘toolbox’ for innovation towards an ecologically, socially, and economically sustainable world.Today, it shapes local, national, and international policies, business model innovation, civil society action, and research agendas. CE research is conducted mainly in the natural sciences and engineering, a social science perspective is still emerging. Despite its widespread use and various findings about its potentials and limitations, the concept and its implementation remain ambiguous. Future research and practice need to reflect on the CE’s goals and associated practices regarding their implications for ecosystems and human well-being and find ways to prioritize strategies accordingly.

Circular economy (CE) is gaining traction in cities as an approach to reducing local and global environmental impacts. Yet, how effective are these strategies in terms of their environmental impacts? To find out, we took a deep dive into 30 CE policies from cities in high-income countries across Europe, the Americas, and Oceania. We assessed the relevance of their indicator sets with regards to their major environmental concerns. To do so, we conducted a qualitative analysis of policy documents published in eight languages, examining common environmental goals, concerns, and progress indicators of various cities. The review reveals a broad spectrum of municipal CE policies, from waste management to climate action. Key concerns include climate mitigation and securing local resource availability, but overall, very diverse environmental targets could be identified. Some of these targets aim at local impacts such as air quality and public health, while others envision global impacts such as biodiversity conservation and intergenerational justice. While greenhouse gas emissions of territorial scope are frequently monitored, the indicator sets mostly ignore that climate mitigation involves a footprint scope. Moreover, the sets mostly lack indicators to monitor other environmental pressures and impacts. To better monitor these, we provide a set of recommendations for research and policy to bridge the gap between environmental concerns and indicator needs. We suggest complementing current resource flow dominated indicator sets with measures of the local environmental state and the application of urban footprint models to help cities monitor the desired global environmental impact of their measures.

Sustainability scientists are increasingly expressing concerns about the lack of creativity and reflexivity, vital elements for driving sustainability transformations, in their profession. We argue that these concerns stem from established scientific practices of knowledge accumulation and interdisciplinary research, often neglecting the influence of group values and disciplinary paradigms. In response, we propose the narrative-led dialog as a tool for sustainability scientists to recognize, analyze and engage with such values and paradigms within interdisciplinary scientific practice. Building upon existing methods, the use of narratives offers scientists an additional way to identify and address the complexities of conflicts, overlaps, and uncertainties inherent in the values and paradigms that guide scientific research and collaboration. This process of revelation can assist sustainability scientists in disrupting traditional academic boundaries, fostering an environment that better nurtures sustainability transformation. Through the narrative-led dialog, scientists can achieve several crucial objectives; they can (1) deepen their scientific practice, (2) identify, discuss and negotiate the underlying values shaping their research, and (3) create an environment conducive to breakthrough ideas, both within their specific fields and across broader sustainability science communities.

Supermarkets play an important role in industrialized food systems, which is why many in academia, politics, industry, and civil society view them as key players in transforming the food system toward greater sustainability. We analyse narratives and proposed solutions in this context, as well as the role of supermarkets in Germany, home to some of the largest retailers worldwide. We show that many actors in the German food system, including supermarkets themselves, perceive the structural problems of overproduction and dysfunctional markets as major obstacles to achieving food system transformation. Despite this, they tend to propose solutions focused on optimization and efficiency in supermarket logistics and retail management or greater consumer awareness. These solutions show little transformative potential. Regarding the structural problem of dysfunctional markets, supermarkets are perceived to be in a quandary due to the drive for profits, competitive markets, and consumer demand. Thus, supermarkets are not likely to drive a transformation of the food system. However, a broadly shared understanding of the core problems of overproduction and dysfunctional markets presents an opportunity for ‘discourse coalitions’ to push for more systemic solutions. The findings may enhance food system stakeholders' understanding of the need for more holistic approaches to addressing sustainability.

The current enthusiasm for the circular economy (CE) offers a unique opportunity to advance the impact of research on sustainability transitions. Diverse interpretations of CE by scholars, however, produce partly opposing assessments of its potential benefits, which can hinder progress. Here, we synthesize policy-relevant lessons and research directions for a sustainable CE and identify three narratives—optimist, reformist, and skeptical—that underpin the ambiguity in CE assessments. Based on 54 key CE scholars’ insights, we identify three research needs: the articulation and discussion of ontologically distinct CE narratives; bridging of technical, managerial, socio-economic, environmental, and political CE perspectives; and critical assessment of opportunities and limits of CE science–policy interactions. Our findings offer practical guidance for scholars to engage reflexively with the rapid expansion of CE knowledge, identify and pursue high-impact research directions, and communicate more effectively with practitioners and policymakers.

Numerous challenges – from population increase to climate change – threaten the sustainable development of cities and call for a fundamental change of urban development and green-blue resource management. Urban forests are vital in this transition, as they provide various ecosystem services and allow to re-shape and re-think cities. Based on a Europe-wide community effort with diverse experts centered around urban forests and urban greening, we propose five key research fields to generate the knowledge required to unlock fundamental changes in urban development and green-blue resource management: circular bioeconomy, climate resilience, governance, social and human environment, and biodiversity. To support the design of greener, cooler, more inclusive and resilient cities, all these research fields require inter- and transdisciplinary collaboration, engaging stakeholders in transforming urban engagement and functioning. We summarise main inter-, trans- und multi-disciplinary research paths for each field and the cross-cutting knowledge areas that can help to address the challenges many cities face (e.g., modelling and assessment of the urban microclimate). For transforming cities further knowledge is needed on e.g., urban innovation, transition, participation, and more. Finally, we address how the identified research gaps can be implemented (e.g., international coordinated research effort, interdisciplinary networks).

The assessment of persistence (P), bioaccumulation (B), and toxicity (T) of a chemical is a crucial first step at ensuring chemical safety and is a cornerstone of the European Union’s chemicals regulation REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals). Existing methods for PBT assessment are overly complex and cumbersome, have produced incorrect conclusions, and rely heavily on animal-intensive testing. We explore how new-approach methodologies (NAMs) can overcome the limitations of current PBT assessment. We propose two innovative hazard indicators, termed cumulative toxicity equivalents (CTE) and persistent toxicity equivalents (PTE). Together they are intended to replace existing PBT indicators and can also accommodate the emerging concept of PMT (where M stands for mobility). The proposed “toxicity equivalents” can be measured with high throughput in vitro bioassays. CTE refers to the toxic effects measured directly in any given sample, including single chemicals, substitution products, or mixtures. PTE is the equivalent measure of cumulative toxicity equivalents measured after simulated environmental degradation of the sample. With an appropriate panel of animal-free or alternative in vitro bioassays, CTE and PTE comprise key environmental and human health hazard indicators. CTE and PTE do not require analytical identification of transformation products and mixture components but instead prompt two key questions: is the chemical or mixture toxic, and is this toxicity persistent or can it be attenuated by environmental degradation? Taken together, the proposed hazard indicators CTE and PTE have the potential to integrate P, B/M and T assessment into one high-throughput experimental workflow that sidesteps the need for analytical measurements and will support the Chemicals Strategy for Sustainability of the European Union.

To effectively navigate out of the climate crisis, a new interdisciplinary approach is needed to guide and facilitate research that integrates diverse understandings of how transitions evolve in intertwined social–environmental systems.The concept of tipping points, frequently used in the natural sciences and increasingly in the social sciences, can help elucidate processes underlying major social–environmental transitions. We develop the notion of interlinked ‘social–climatic tipping points’ in which desirability and intentionality are key constitutive features alongside stable states, feedbacks, reversibility and abruptness.We demonstrate the new insights that our interdisciplinary framework can provide by analysing the slowdown of the Atlantic Meridional Overturning Circulation and associated flooding of the Ahr Valley in Germany as a social–climatic tipping point.This framework can enable more sustainable and equitable futures by prioritising social–climatic tipping points for interdisciplinary research, identifying opportunities for action, and evaluating the nuanced desirability and acceptability of proposed solutions.

The assessment of persistence (P), bioaccumulation (B), and toxicity (T) of a chemical is a crucial first step at ensuring chemical safety and is a cornerstone of the European Union’s chemicals regulation REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals). Existing methods for PBT assessment are overly complex and cumbersome, have produced incorrect conclusions, and rely heavily on animal-intensive testing. We explore how new-approach methodologies (NAMs) can overcome the limitations of current PBT assessment. We propose two innovative hazard indicators, termed cumulative toxicity equivalents (CTE) and persistent toxicity equivalents (PTE). Together they are intended to replace existing PBT indicators and can also accommodate the emerging concept of PMT (where M stands for mobility). The proposed “toxicity equivalents” can be measured with high throughput in vitro bioassays. CTE refers to the toxic effects measured directly in any given sample, including single chemicals, substitution products, or mixtures. PTE is the equivalent measure of cumulative toxicity equivalents measured after simulated environmental degradation of the sample. With an appropriate panel of animal-free or alternative in vitro bioassays, CTE and PTE comprise key environmental and human health hazard indicators. CTE and PTE do not require analytical identification of transformation products and mixture components but instead prompt two key questions: is the chemical or mixture toxic, and is this toxicity persistent or can it be attenuated by environmental degradation? Taken together, the proposed hazard indicators CTE and PTE have the potential to integrate P, B/M and T assessment into one high-throughput experimental workflow that sidesteps the need for analytical measurements and will support the Chemicals Strategy for Sustainability of the European Union.

The current enthusiasm for the circular economy (CE) offers a unique opportunity to advance the impact of research on sustainability transitions. Diverse interpretations of CE by scholars, however, produce partly opposing assessments of its potential benefits, which can hinder progress. Here, we synthesize policy-relevant lessons and research directions for a sustainable CE and identify three narratives—optimist, reformist, and skeptical—that underpin the ambiguity in CE assessments. Based on 54 key CE scholars’ insights, we identify three research needs: the articulation and discussion of ontologically distinct CE narratives; bridging of technical, managerial, socio-economic, environmental, and political CE perspectives; and critical assessment of opportunities and limits of CE science–policy interactions. Our findings offer practical guidance for scholars to engage reflexively with the rapid expansion of CE knowledge, identify and pursue high-impact research directions, and communicate more effectively with practitioners and policymakers.

Following a long-standing and highly contested policy debate, in June 2021, the German parliament passed the Supply Chain Due Diligence Act requiring mandatory due diligence (MDD) of large companies, holding them accountable for the impacts of their supply chain operations abroad. Applying the discursive agency approach and using evidence from policy documents and 21 interviews with key stakeholders, we analyze the political strategies that paved the way toward MDD in Germany. The decisive strategy was an innovative benchmarking and monitoring mechanism that provided the legitimacy for a law and opened a window of opportunity for MDD supporters. Civil society and supportive politicians used this window of opportunity to build broad political coalitions that included the support of some companies. We discuss the ramifications of these findings for understanding the domestic politics behind the newly emerging norm of foreign corporate accountability.

China and the European Union (EU) signed the first international circular economy (CE) agreement shortly after China issued the ‘Waste Ban’ (WB) on the import of 24 categories of solid waste. While the WB gained global attention, limited research addresses its political implications for international CE. Based on 72 expert interviews, 52 documents and participant observation, we study political WB narratives and corresponding perceptions of ‘Chinese’ and ‘European’ agency in the China-EU case. Our results show a political gridlock in China-EU CE coordination: the main narratives on the WB diverge on the very roles and rules of CE cooperation, scales of implementation, and the assessment criteria for environmentally and socially sustainable CE(s). To enable fruitful CE cooperation, we suggest three critical points for reflection and negotiation: (1) overcome ‘student–teacher’ roles rooted in linear development that run counter to CE ideas; (2) reconsider the focus on international and national waste diversion, instead of local waste prevention, that propels global waste markets sustained by increasing waste volumes; and (3) evaluate both the benefits and impediments of (new) trade relations for a CE cooperation that contributes to environmental and social sustainability.

Lock-in mechanisms are major hurdles to sustainability transitions. Scholars identified various types of lock-ins; however, their dynamics and interactions remain underexplored. Using the case of food packaging, this study enhances the conceptual understanding and empirical analysis of lock-ins and their interactions from a socio-technical perspective. We analyze the material, institutional, behavioral, and discursive configuration and the shallow and deep lock-ins reinforcing the persistent dominance of single-use over reusable food packaging in Germany. Additionally, we explore the lock-in interactions both within and between the socio-technical elements. Hence, we introduce archetypical interlock-ins and lock-in clusters pointing to core trends of resistance towards reusable packaging alternatives. This study advances the lock-in concept for future socio-technical analyses while guiding the illumination of the complex dynamics of stability, the assessment of current sustainability transition interventions, and the search for potential unlocking strategies to enable change.

Understanding the dynamics of stability and change is key to accelerate sustainability transitions. This paper aims to advance and inspire sustainability transition research on this matter by collecting insights from interpretative environmental discourse literature. We develop a heuristic that identifies and describes core discursive elements and dynamics in a socio-technical system. In doing so, we show how the interplay of meta-, institutionalized, and alternative discourses, dominant, marginal, and radical narratives, as well as weak and strong discursive agency influence the socio-technical configuration. The heuristic suggests three discursive lock-ins reinforcing the stabilization of socio-technical systems: unchallenged values and assumptions, incumbents’ discursive agency, and narrative co-optation. Furthermore, it explores three pathways of discursive change: disruptive, dynamic and cross-sectoral. Overall, this paper puts forward a discursive perspective on sustainability transitions. It offers additional analytical approaches and concepts for discursive transition studies, elaborated insights on the dynamics within and between the analytical dimensions of a socio-technical system, as well as a theoretical baseline for analyzing discursive lock-in mechanisms and pathways of discursive change.

A paradigm shift is needed in wastewater treatment plants (WWTPs) to progress from traditional pollutant removal to resource recovery. However, whether this transformation produces overall environmental benefits will depend on the efficient and sustainable use of resources by emerging technologies. Given that many of these technologies are still being tested at the pilot scale, there is a lack of environmental assessments quantifying their impacts and benefits. In particular, an integrated approach to energy and nutrient recovery can elucidate the potential configurations for WWTPs. In this study, we conduct a life cycle assessment (LCA) of emergent wastewater treatment technologies aimed at increasing resource circularity in WWTPs. We focus on increasing energy self-sufficiency through biogas upgrades and a more radical circular approach aimed at nutrient recovery. Based on a case-study WWTP, we compare its current configuration with (1) implementing autotrophic nitrogen removal in the mainstream and deriving most of the organic matter for biogas production, which increases the quality and quantity of biogas available for energy production; (2) implementing struvite recovery through enhanced biological phosphorus removal (EBPR) as a radical approach to phosphorus management, offering an alternative to mineral fertilizer; and (3) a combination of both approaches. The results show that incremental changes in biogas production are insufficient for compensating for the environmental investment in infrastructure, although autotrophic nitrogen removal is beneficial for increasing the quality of the effluent. Combined phosphorus and energy recovery reduce the environmental impacts from the avoided use of fertilizers and phosphorus and the nitrogen release into water bodies. An integrated approach to resource management in WWTPs is thus desirable and creates new opportunities toward the implementation of circular strategies with low environmental impact in cities.