Phosphates are essential components of any efficient fertilizer. Natural phosphate rock is, however, not available in every part of the world. According to the European Commission, phosphate rock has high economic importance as well as a certain supply risk--at least for Europe. For these reasons, environmental technology research has received a great attention from the stakeholders that provided support in developing processes for recovering phosphate from wastewater and sewage sludge to help to close the phosphate cycle and reduce potential risks, including eutrophication and its influence on the environment. In this paper, we present a design case study of integrating the idea of phosphate recovery into chemistry education via a nonformal learning experience for high school students in Germany. The paper discusses a series of experiments and shows how they were embedded through interdisciplinary curriculum development.