The emergence of a commons in urban sanitation: urine-diverting dry toilets in participatory housing

Human excrement contains elements that can be used in agriculture (carbon, phosphorus, nitrogen…). The widespread use of sewerage following the urban development during the 20th century has massively oriented their management towards linear modalities generating negative environmental externalities. This logic is called into question. Source separation projects have been carried out in Sweden since the 1990s. Interest in this practice is now growing in France, with building or neighbourhood development projects considering the implementation of excreta collection and recovery systems. These projects re-examine urban sanitation from a technical, organisational, social and territorial point of view: the decentralised level, that was defined as a source of waste, becomes a resource producer, thus enabling inhabitants to initiate a reclaiming process.
The dynamics of co-housing seems to provide a privileged framework for experimenting with separation at source in the city, by inserting it into a logic of commons. This can be seen in the case of the Au clair du Quartier building in Grenoble, inhabited since 2017 by five families who have adopted separating dry toilets in their apartments and the composting of faecal matter in their shared garden. This article analyses the conditions that led to this choice, as well as the rules adopted in order to keep these technical devices functional. This example raises questions about the changes in the urban sanitation system that could be brought about by the development of source separation projects such as the one in Au Clair du Quartier. A third way is thus emerging between non-collective (individual) and collective (public) sanitation, with groups of inhabitants and users who take part in the production of the sanitation service, inviting us to think about the implementation of new commons in the management of flows in urban areas.