This paper seeks to better understand urban sustainability experimentation with reference to the bodily sensations of composting household food waste. Taking our lead from Deleuze and Guattari, we argue that experimentation is not just the result of the scientific knowledge of how to compost, but the sensations of bringing together materials, human, non-humans, and ideas into a working arrangement. We draw on Deleuze and Guattari's notion of molar, molecular and rupture lines to offer a way to envisage experimentation as an affective dimension that emerges from the opposing forces that dissolve and support bodily capacities to care for compost as working socio-material arrangements that make, remake, and unmake composting bodies and spaces. Based on a sensory composting ethnography conducted with 21 individuals of European ancestry and tertiary education in Wollongong, New South Wales, Australia, we provide two significant insights. First, we argue that implications for the bodily capacity to care for compost are discerned from the sensations of molar lines of scientific household food waste management. The subjectivities and backyard territories created by the affective intensities of composting occur along molar lines of environmental citizenship that are narrated as pleasure, satisfaction, and love. Second, we illustrate how composting experimentation involves a heightened sensation of the self in backyards, through molecular lines generated by the presence of certain smells, temperatures, food waste, plants or animals that challenged the liveable order of backyards. We advance geographical scholarship by bringing new ways of approaching household sustainability transitions by conceiving of experimentation from the perspective of molar and molecular lines and how these may be used to apprehend sensations which stabilise, or undo, a sense of self and place.