This article explores the technoenvironmental politics associated with government-sponsored climate change mitigation. It focuses on England’s New Technologies Demonstrator Programme, established to test the “viability” of “green” waste treatments by awarding state aid to eight experimental projects that promise to divert municipal waste from landfill and greenhouse gases from the atmosphere. The article examines how these demonstrator sites are arranged and represented to produce noncontroversial and publicly accessible forms of evidence and experience and, ultimately, to inform environmental policy and planning decisions throughout the country. As in experimental science, this process requires that some bear witness to the demonstrators, but in a disciplined way. Whether through the extrapolation of facts about technical performance by affiliated third-party consultants, or the orchestration of visitor centers open to the general public, making the demonstrators public involves controlling the ways in which they are interpreted and perceived. However, the unstable publicity of waste management facilities proliferates unofficial accounts as well. These acts of counterwitnessing, as I refer to them, not only potentially dispute the official evidence collected from the demonstrators, they also can pose a challenge to the understanding of technology upon which such government initiatives are based.