Recycling nutrients contained in human excreta to agriculture: Technology options, trends, and readiness

Circular nutrient solutions can make important contributions to improve fertilizer availability and reduce nutrient losses from waste management. This paper focuses on the recovery of plant nutrients (notably nitrogen, phosphorus, and potassium) found in human excreta and domestic wastewater for reuse in agriculture (as crop fertilizer, for fertilizer production, as animal feed, or for the production of microbial protein). Based on over 14 000 research papers previously identified through a suite of reviews and systematic maps, technology options that have been researched are articulated and research trends discussed. Based on among others a catalogue of nutrient recovery technologies provided by the European Sustainable Phosphorus Platform (ESPP), technological solutions and their readiness are mapped onto the identified technology options. Across many technology options, in addition to ongoing research activity, a range of technological solutions are available on the market. While there likely still is scope for additional research, it would appear there is even more scope for implementing available circular nutrient solutions at scale.