This paper argues that “new” sustainable technologies being used to manage human waste—composting toilets, bioremediation, and biodigestion—are essentially reviving the medieval strategy of waste management: containment and reuse of waste, as opposed to the modern strategy of dilution and evacuation. This debate should not occur in a vacuum, uninformed by the motivations for, and history of, the development of the modern system. Therefore, this paper more closely examines the medieval system, which closely linked waste and agricultural production. It then considers the transformation to the modern system, using the design of Leonardo da Vinci’s city of Romorantin as a case study. It is argued that this transformation was largely predicated on now-delegitimized miasmic theory, which held foul or corrupt air to be the cause of disease, and that it precipitated larger changes in the urban environment. In light of this historical view it is suggested that contemporary sustainable technologies imply larger changes in the form of human settlement, and that the nature of these changes must be explored further.