This essay traces a scientific pilot project to transform the black soldier fly (Hermetia illucens) into a biotechnology to treat urban organic waste in accordance with the dominant cultural logics of an ecologically modern approach to waste management in contemporary China. A principle of urban waste management, circularity, and a spatial logic of urban living, enclosures, condition the scientific intervention that promises to harness animal metabolic labor as a biotechnology and a waste infrastructure that can be adapted to the urban ecologies of Guangzhou. While scientists emphasize the natural proclivities of insect metabolism to transform waste into value, my ethnographic research illustrates that the practice of aligning animal metabolism with urban metabolism is anything but natural or automatic. Together, circularity and enclosure, as guiding logics of waste management in Chinese ecological modernization, uphold a fiction of biocapital; they create the illusion that nature generates value and remediates environments without human intervention while mystifying and naturalizing the appropriation of nature and labor in the new green city.