Phosphorus recovery—recent developments and case studies

Phosphorus is an essential nutrient and a nonrenewable dwindling resource, yet it is also a potential environmental pollutant. The spread of modern agriculture to increase food production has put natural reserves under strong pressure. At the same time, the excessive losses of phosphorus have caused worldwide eutrophication phenomena in many water bodies. To obtain a sustainable phosphorus supply and environmental conservation, more than 30 technologies have been developed to recover phosphorus from waste streams in the view of circular economy, replacing phosphorus from phosphate rocks. Wastewater, sewage sludge, and sewage sludge ashes have been shown to be promising alternative sources. Yet only a few technologies have been implemented at full scale, limited by economic feasibility, environmental risks, and regulations. This chapter will explore in detail the latest knowledge on recent approaches to recover phosphorus, with a specific focus on new case studies, wet extraction from sewage sludge ashes, and from hydrothermal carbonization slurries.