A key challenge for implementation of a circular economy model in manufacturing systems is the functional dependence of downstream processes on upstream byproducts. Design principles provide a framework for mapping goals to solutions by decomposing complex engineering problems into structured sets of requirements to be satisfied and embodied by design parameters and process variables. Large Language Models can computationally represent such textually-described design elements to quantify interconnections between problems, solutions, and processes. We present a Functional Digital Twin concept, powered by AI language modeling and guided by principles of manufacturing systems design, to identify functionally coupled process variables in an industrial symbiosis and automatically push alerts to stakeholders in a circular manufacturing system. Changes in byproduct composition are pushed downstream, and upstream decision-makers are guided to balance satisfying their design requirements with maintaining circularity of the system. The presented method is demonstrated in a case study of bio-based absorbent materials for intended use in disposable sanitary articles developed from byproducts of the agro-food industry.

The ‘decade of action’ intended to accomplish the ambitious 17 Sustainable Development Goals (SDGs) faces notable challenges. Our investigation into the impact of the COVID-19 crisis on SDG progress reveals important lessons for shaping effective policy interventions to ensure resilient societies and overall well-being. Through systematic mapping and a rapid review approach, our analysis reveals that nearly 90% of the SDGs, specifically 144 targets, were adversely affected by the COVID-19 pandemic. Yet, there is a glimmer of opportunity: 66 targets stand to gain from the crisis-induced transformations, provided that the right choices are made. Achieving this goal demands a comprehensive approach and decisive leadership to steer an inclusive economic recovery that also safeguards the environment while safeguarding the environment. The intricate interplay between the ongoing planetary and post-COVID-19 crises, environmental challenges, and conflicts underscores the need for a proactive, deliberate and well-informed approach, marked by collaborative decision-making, which is imperative for effectively steering the ‘decade of action’ toward achieving the SDGs. These complex challenges demand collective, decisive action, all with the overarching aim of securing a just and sustainable future for all.

The valorisation of urban biowaste can contribute to a circular and sustainable resource management. However, biowaste valorisation is not inherently sustainable. This study employs the Sustainable Development Goals (SDGs) to investigate the sustainability implications of biowaste valorisation. A narrative literature review provided an overview of the current scientific knowledge on interactions between biowaste valorisation and selected SDG targets. Then stakeholder interviews yielded insights into such interactions in a national context. Our findings show the potential for 19 synergies and 11 trade-offs between biowaste valorisation and 20 selected SDG targets that are addressed in detail. Although the synergies outnumber the trade-offs, different context-dependencies influence the nature and strength of the interactions. We highlight three types of context-dependencies relating to governance. This study informs the scientific community and decision-makers on planning for sustainable biowaste valorisation that addresses context-dependencies. The insights can guide countries and cities at early transition stages towards biowaste valorisation.

The role of electric vehicles (EVs) in more sustainable cities is widely recognized, with their adoption increasing rapidly. Most governments have targets for continued EV adoption rate growth, and some plan to ban fossil-fuelled vehicles altogether. Yet, in most countries, including Brazil, the proportion of EVs among new vehicles sold remains low. EV adoption poses multiple technological, economic and social challenges that require targeted policy mechanisms. This study assesses policy measures to expedite EV adoption for road transport decarbonisation and sheds light on the critical role of EVs in sustainable urban development. We explore electric mobility challenges in urban areas, focusing on the case of Curitiba City in Brazil. We investigate existing challenges and barriers to policy implementation in Curitiba and successful interventions in cities worldwide to identify suitable policies for Curitiba. The study uses in-depth interviews with relevant stakeholders to examine policy tools, including financial, legal, knowledge-based, and societal instruments. The study recommends complementary instruments and measures to accelerate their adoption in Curitiba. Overall, the study's results, which identify criteria for policy design and implementation towards complete transport decarbonisation, should be valuable for decision-making in transport and mobility planning.

The circular economy (CE) model, where resources are kept "in the loop" for as long as possible through a series of reusing, remanufacturing, recycling, and recovery strategies, has been acclaimed for reducing the environmental impacts of our current economic model substantially and has therefore been supported by a wide range of policymakers as one solution to tackling climate change. However, how circular transitions in cities impact people has been rarely researched, and even less attention has been paid to the negative consequences of CE transitions.

This paper presents the findings from a social impact assessment conducted in the city of Umeå, Sweden. We identified several negative impacts of a CE transition across seven social impact categories and explored three areas in depth with stakeholders in the city: employment, access to services and participation. We found that the negative impacts of the CE are perceived to be limited and that the CE interventions are mainly viewed as a win-win-win outcome, i.e., a win for the environment, the economy and people. This raises questions about the level to which societal consequences have been considered and whether all relevant stakeholders, in particular civil society, have participated in the design of the city's CE strategy. Our findings can inform other cities about possible negative consequences of CE transitions and provide insights into how to incorporate different stakeholders in the CE transition process to ensure that no one is left behind.

As cities worldwide implement strategies to accelerate the transition toward a circular economy (CE), there is an increasing need for tools to monitor progress. However, a standardised metric for CE monitoring in urban areas is lacking. This study examines the potential of the EU Circular Economy Monitoring Framework (CEMF), an established indicator-based framework for measuring national- and EU-level circularity performance, as a monitoring tool for urban areas. For this purpose, available data sources that can support the framework's application at the urban level are mapped, and data quality is assessed following the pedigree matrix approach. Next, the CEMF indicators are computed for the urban area of Umeå, Sweden. The mapping showed limited availability of urban-level data, necessitating the downscaling of national-level data using proxy factors. Most available urban-level data are of high quality, while the quality of national-level data is reduced when used to compute indicators at the urban level. The application of the CEMF in Umeå indicates that there are areas where the municipality performs well, though further improvements are needed. We conclude that the CEMF has potential as a monitoring tool for urban areas. However, improvements in CEMF...s scope and data availability are recommended.

Worldwide, cities are implementing circular economy (CE) strategies to reduce the resources they consume and their environmental impact. To understand the CE strategies and sectors cities have been focusing on, we have conducted an evidence map describing the literature published in the last ten years. The main outputs are a searchable database comprising 178 publications showing which cities have been discussed, what CE strategy they are focusing on, and the sectors under review. The results show that most research has focused on European countries. Those efforts mainly concentrate on waste and wastewater management, and recycling and recovery strategies are considered the “lower-level” strategies in the CE taxonomy. It highlights the potential for further research in other cities and regions, looking across sectors and analyzing strategies that tackle the “higher-level” CE strategies. Higher-level strategies include reducing, repurposing, remanufacturing and reusing opportunities to achieve the potential attributed to a CE model by governments across the world.

The transition towards a circular economy (CE) is increasingly recognized as a promising pathway to tackle pressing sustainability challenges at the city-level. Indicator-based frameworks, that is, integrated systems of indicators, are considered as useful tools for monitoring this transition. Yet, studies that map and assess such frameworks are scanty. This article addresses this gap by assessing 15 indicator-based frameworks applicable to measure circularity at the city-level. The identified frameworks were assessed using eight criteria (transparency, stakeholder engagement, effective communication, ability to track temporal changes, applicability, alignment with CE principles, validity and relevance to sustainable development). Additionally, 12 validity requirements were defined to assess to what extent the indicators in the frameworks reflect CE aspects. The assessment reveals a wide variation regarding the extent to which the frameworks match the criteria with none of them satisfying all. In addition, in terms of validity criterion, none includes indicators that fulfill all the validity requirements. Furthermore, most frameworks consist mainly of environmental indicators and only three include indicators reflecting aspects related to the four pillars of sustainable development (environmental, social, economic and governance). Further research could develop a standardized framework for measuring circularity at the city-level and improving existing frameworks.

In this chapter, we discuss why in food waste and loss and energy debate community-led initiatives and alternative economies deserve to be looked at more seriously when considering support to circular economy approaches, modelling, and adaptation in the urban context. We focus on the emergence of two types of community-led initiatives in the energy and agri-food sectors. We draw parallels between their role in bringing variety to experimentation when applying circular economy principles in practice. To better understand the potential of combining alternative urban agri-food networks with community-led energy initiatives in sustainable transformation of urban production and consumption systems, it is important to recognize that the uptake of visions or strategies of circularity is affected by the availability and strength of social networks, driving forces behind their emergence and persistence, and technological solutions within and for these grassroots initiatives. We recognize three conditions to building resilient sustainable urban food networks: understanding of multiple urban flows from a coupled systems-perspective, the diversification of knowledge, and overcoming structural and cultural resistance to change. Different framings, such as in narrow terms of innovations focused on technological optimisation, can slow down recognition and reaping benefits from interdependencies of food and energy infrastructures, networks, and institutions. We argue that there is a need for better understanding of how can measures directed at minimizing food waste and loss and wider uptake of sustainable energy systems be coupled and complementary in a more circular urban economy.