Achieving sustainable biowaste management is a key challenge for cities worldwide. In this context, biowaste valorization is an indispensable option for managing unavoidable biowaste and reducing the associated methane emissions. Several innovations that enable biowaste valorization are technologically mature. However, their implementation is still limited in most cities around the world. Therefore, it is essential to better understand the different pathways towards implementing biowaste valorization. This paper presents a case-study of two countries at different phases in their transition to biowaste valorization: Sweden as a case at a mature phase and Greece as a case at a formative phase. We apply the Technological Innovation Systems framework to investigate how innovation systems for biowaste valorization develop and associated path-dependencies. Our findings show that various path-dependence lock-ins can occur at different transition phases. Our empirical insights suggest that a focus on the diffusion of certain mature innovations can support the growth of biowaste valorization systems. However, it can also lead to path-dependence lock-ins that influence the systems’ resilience to shocks. We thus recommend decision-makers to pursue balance between the rapid diffusion of mature innovations for biowaste valorization and parallel support for experimenting with more radical innovations to harness the systems’ resilience to shocks.

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 potential contribution of decentralized approaches in implementing biowaste recovery systems has attracted interest in urban policy making and scientific research. Although the scientific literature on the topic is rapidly increasing, it is still limited and scattered. A comprehensive overview of current scientific knowledge is thus needed to support future research on decentralized options for biowaste recovery systems. Anaerobic digestion (AD) is a mature biowaste treatment technology that recovers energy and nutrients, and can close urban resource loops. Through a scoping literature review, this paper investigated decentralized AD and its potential contribution in implementing urban biowaste recovery systems. We identified opportunities and challenges for planning of decentralized AD, and concluded that these mainly concern: (a) digestate management; (b) the potential for local circularity with product valorization in outlets such as urban agriculture; and (c) the development and application of decision support tools. The findings highlighted the need to enhance scientific evidence on the impact of decentralized AD in different urban contexts. Results from published studies were highly context-specific, making it difficult to draw general conclusions. This study can support the transition to integrated planning of AD and wider urban biowaste recovery systems. Such planning must include a comprehensive analysis of configuration approaches.

Biorefineries have attracted interest in research and practice for their potential contribution to sustainable bioeconomies. This paper addresses municipal biowaste as a feedstock that can be integrated into biorefineries but remains under-researched. We explore the integration of biowaste as a feedstock in biorefineries drawing empirical insights through a stakeholder survey and follow-up interviews with Swedish stakeholders. Our findings show positive attitudes towards biowaste integration. However, it is not a current target of Swedish stakeholders. The respondents ranked highly several challenges related to biorefinery development and biowaste integration, particularly in terms of the investments required for such endeavours. We argue that in pursuing key Swedish goals such as increasing domestic biogas production and biorefinery development, there is an opportunity to rethink visions and narratives for the Swedish bioeconomy. In this context, biowaste can be considered together with other biomass residues and contribute towards feedstock acquisition for sustainable biorefinery development. Our insights from the Swedish case highlight the importance of transdisciplinary collaboration to cross the valley of death for biorefinery development from pilot to commercial scale. Private actors are highly responsible for making the relevant investments, but require policy and financial support from the public sector. In this context, the role of the scientific community and different bioeconomy arenas is crucial in connecting the different types of actors and developing common vocabularies and agendas. These insights can inform other cities and countries for the development of their bioeconomies and biowaste management.