The bioeconomy aims to respond to current and future food, climate and ecological challenges. However, although the bioeconomy is based on the valorisation of biological resources, it may not be sustainable (Axelos et al, 2020). To meet all the challenges faced by food systems, the bioeconomy must be sustainable and circular (Axelos et al, 2020). Against this background, the urban context raises many specific questions linked in particular both to population density (pollution, space occupation, etc.) and to the characteristics of the flow of materials specific to cities (food supply to cities, management of effluents, and waste). This communication is part of a project that studies the development of sustainable and circular environmental biorefinery projects in urban areas. These projects could be characterized in particular by (1) the valorisation of urban bio-waste via cascading approaches, (2) the small size of the biorefinery units and (3) the local added value to the products of the biorefinery. While currently, some biorefinery units exist in France, e.g. La Mède and Bazancourt-Pomacle, these are large-scale and transform agro-resources and not urban waste. In view of the current non-existence of urban environmental biorefineries, the objective of this article is to shed light on the challenges of such future projects, the possible business model innovations with regard to the specificities of these projects, and their risk and success factors. To do this, several existing cases of micro-breweries and composters are studied, which both are characterized by 14 their industrial micro-size, the supply of organic resources, and the location within an urban area. After proposing a framework for analyzing circular business models and their success or failure factors (Donner et al, 2021), the results of a scientific review on these projects and of a study of several concrete micro-breweries and composter cases in France are presented. They show that the value proposition can consist of innovative products (in the case of micro- breweries), in particular putting forward the territorial dimension attached to beer; or the proposition of new local products and services, in the case of micro-composters, with, again, a valorisation of the local origin of the compost. The cases studied and the scientific references highlight the challenges related to the biowaste supply: the need to secure it, and to deal with its inherent agronomic characteristics for an optimal transformation. The micro-enterprises also face economic challenges linked to their small size such as significant investment costs and competition from large enterprises that are already well established in the markets. Finally, a key element of success is the involvement of different local stakeholders, calling for organisational as well as social innovations.