Progressing Circular Economy in the Nordic Countries: Phosphorus Recovery from Secondary Resources

Phosphorus is an essential element to sustain life; it is a building block of cells and a vital nutrient for plants, animals, and humans alike. The vast majority of phosphorous originates from phosphate mines and is consumed as fertilizer. As a finite and non-renewable resource, phosphorus faces increasing scarcity, while demand is rising due to population growth and the demand for food. At the same time, a lot of phosphorous is lost in use, e.g. as runoff from agriculture, leading to the pollution of aquatic ecosystems, the most important example being the eutrophication of Baltic Sea. Therefore, phosphorus recovery and recycling will not only reduce environmental pollution, but also safeguards global food security and promotes the wellbeing of ecosystems.
This doctoral study investigates the potential of phosphorus recovery in the Nordic countries. The research includes systematic review methodologies, as well as a life cycle assessment study. The work describes the drivers and barriers of sustainable phosphorus management, the secondary resources of phosphorus, available recovery technologies and a case study of phosphorus recovery from sewage sludge.
The results of this research highlight a significant potential for phosphorous recovery in the Nordic countries from sewage sludge, agricultural waste, and mining residues. The life cycle assessment conducted for sewage sludge treatment shows that anaerobic digestion combined with pyrolysis offers the most sustainable solution from both a waste management and nutrient recovery point of view. Pyrolysis destroys microplastics, it yields biochar, a potential nutrient source, and also generates energy. Therefore, the combined anaerobic digestion and pyrolysis method supports the circularity of phosphorous, as well as sustainable use of natural resources and environmental protection.