TU.2.B || Future Sustainable Lifestyles – Urban Structure

Tanguy, Audrey; Laforest, Valérie; Glaus, Mathias

The transition to a circular economy in Western countries calls for a return to fine-scale management of urban flows. While our current linear economy relies on centralized and mostly external urban metabolisms, a higher degree of circularity implies a reconfiguration of urban infrastructure to some extent, with public authorities and citizens aiming to take advantage of local and accessible resources. This trend is especially visible in urban waste management systems, where highly decentralized solutions (e.g. home-composting) emerge and are promoted by municipalities next to more conventional centralized treatment sites (e.g. incinerators). Nevertheless, although a higher degree of decentralization is desirable, the extent of this spatial reconfiguration and its environmental benefits are not clear. One of the main reasons is that the “proper” plants’ size and degree of decentralization of waste management systems is highly dependent on the context, on the amount and type of waste produced and their location. But it should also depend on the city’s needs for recovered materials and/or energy if the objective is to create real local circular loops at the urban level. The aim of this work is therefore to assess how the city’s needs for secondary materials obtained from its waste management system can influence the system’s spatial configuration and its environmental impact. To meet this objective, a territorial approach for waste management developed by the authors is used on a Canadian case study, the composting of the organic fraction of Montreal’s urban waste. Two scenarios of compost use are compared. The first scenario models the current situation, where compost is mostly exported. The second includes uses of compost for community gardens, urban agriculture and municipal parcs. Results show that accounting for local uses of recovered products helps decision-makers to plan adapted waste management solutions, which tends to decrease the system’s impact.