AbstractAssuming communities in a city may formally express their aspirations for the future sustainability of their city, which technological innovations for changing the city's infrastructure and metabolism might they introduce today, as a first step towards realizing their distant aspirations? What is more, recognizing the diversity of aspirations that may never be reconciled into a consensus, might some innovations and policy interventions be nevertheless more privileged than others, in being non-foreclosing? How might we discover this? These questions are addressed through a computational case study of London. The city's metabolism is modeled as the set of interacting, cross-sectoral (water, food, energy, waste) flows of carbon (C), nitrogen (N), phosphorus (P), water, and energy. Given various degrees of target improvements in an accompanying set of metabolic performance metrics, and given four candidate technological innovations in the water sector, an inverse (or “backcasting”) analysis is implemented in order to identify the key technological, policy, social, and climate-related features determining whether the community's aspirations — through the surrogates of the metabolic performance metrics — are attainable (or not), under substantial uncertainty. From this, the paper proceeds to examine which businesses are currently marketing some of the so-identified key technological innovations. It closes with a brief review of the related status of the economic justifications and social changes that may either promote or stifle the opportunities for London to move towards a higher niveau of sustainability.