The spatial impact of socio-technical transitions - The case of phosphorus recycling as a pilot of the circular economy

Socio-technical innovations for the recovery of phosphorus (P) from sewage sludge (ashes) and the recycling of the secondary material in the agri-food system have been gaining prominent roles in current debates on circular economy. While research has been primarily focusing on questions on technical feasibility, the impact of the innovations on the social and material structures of the underlying socio-technical wastewater and agri-food systems has been receiving less attention. Drawing on theoretical insights from transition theory and empirical data from expert interviews, our analysis of two approaches to P recycling - phosphoric acid and struvite - shows how innovations create different spatial structures of actors, institutions, infrastructure, and material flows and in doing so promote or hamper fundamental changes in the socio-technical systems. In the wastewater system, both approaches foster the incumbent socio-technical regime of centralized wastewater treatment. In the agri-food system, on the one hand, the phosphoric acid approach supports large-scale industrial structures comprising the fertilizer industry and global P flows fostering the incumbent globalized agri-food regime. On the other hand, struvite facilitates the local distribution of fertilizers between wastewater treatment plants and farmers and supports small-scale P cycling providing opportunities for a structural reconfiguration of the agri-food system.