Techno-economic analysis of struvite and ammonium sulphate recovery from source-separated urine at multi-university scale

Conventional nitrogen fertiliser production via Haber–Bosch process is highly resource-intensive, while phosphorus fertilisers rely on phosphate rocks, a finite resource vulnerable to depletion. Human urine contributes only 1% volume of domestic wastewater, contains a large fraction of nutrients present in wastewater, highlighting its potential for source-separation and nutrient recovery. Struvite precipitation and ammonia stripping have been widely demonstrated at laboratory scales as effective methods for nutrient recovery; nevertheless, translation to large-scale implementation remains limited, due to lack of robust, quantitative techno-economic evidence. This study presents a techno-economic evaluation of struvite precipitation, ammonia stripping, and their sequential integration. The facilities were designed to treat 41.1 m3/day of source-separated urine, corresponding to the estimated urine generation from four universities in Dublin, Ireland. The integrated facility recovered both phosphorus (78%) and nitrogen (66.4%), while standalone struvite precipitation and ammonia stripping facilities achieved 78% phosphorus and 71% nitrogen recovery, respectively. Economic evaluation revealed that the integrated facility had a payback period of six years under conservative conditions, compared to fourteen and twenty-seven years for ammonia stripping and struvite precipitation, respectively, despite requiring the highest capital and operational expenditure. Struvite precipitation demonstrated the longest payback periods and negative net present values across multiple scenarios. Beyond financial benefits, the implementation of such facilities can alleviate nutrient loading on wastewater infrastructure, enhance fertiliser supply resilience, and support sustainable resource management. Further research is necessary to determine the commercial demand for urine-derived fertilisers, as well as the additional costs of micro-pollutant removal.