At the Dutch summer festival Lowlands earlier this month, Chris Slootweg, Bas de Jong and Steven Beijer examined the urine of visitors. The aim of their project was to see whether residual products from pharmaceuticals and chemicals end up in the phosphate recovered from urine. The 'struvite' recovered from the urine can serve as fertilizer for agricultural purposes, or it can be used as a renewable resource for the production of high-value phosphate products, such as flame retardants.