Phosphorus is one of the essential nutrients needed for global food security. However, the phosphate life cycle is currently predominantly linear, from phosphate mining to fertilizer production, agriculture, food consumption and wastewater treatment. Excess phosphorus ends up in soil and in agricultural run-off.

Problems of eutrophication due to this run-off, coupled with the limited remaining commercial phosphorus reserves in the world, argue strongly for a transition towards a circular economy for phosphorus in many populated drainage basins, such as the Baltic Sea region.

To identify barriers and opportunities for such a transition, the authors employ an analytical framework that merges an innovation systems perspective with elements from socio-technical transitions literature.

They find that lack of appropriate policy steering and insufficient knowledge on the performance of technologies for reuse remain key obstacles for closing the phosphorus loop in the Baltic Sea region. The new European Union Fertilizing Products Regulation presents structural opportunities that are likely to level the playing field between conventional and waste-derived fertilizers and thereby improve the market opportunities for recovered phosphorus.

However, the system currently appears to be moving towards a narrow focus on a few new technologies for recovering and reusing phosphorus, which could lead to new lock-ins.  Solutions need to address the acceptability of the technologies and waste-derived products to users, while the vision of a circular economy needs to be better articulated through government interventions to capture the environmental externalities of phosphate mining.

The authors also highlight the value of recycling other nutrients and organic matter in wastewater, and the importance of “upstream” work to reduce the contaminants entering wastewater streams at the source as a way to minimize the public health and ecosystem risks associated with reuse and wastewater management more broadly.

The paper further highlights knowledge gaps and proposes recommendations for policy and research related to developing a circular phosphorus economy.