This paper offers a counterpoint to the prevailing account of waste in the human sciences. This account identifies waste, firstly, as the anomalous product of arbitrary social categorizations, or ‘matter out of place’, and, secondly, as a distinctly human way of leaving behind and interpreting traces, or a mirror of culture. Together, these positions reflect a more or less constructivist and anthropocentric approach. Most commonly, waste is placed within a framework that privileges considerations of meaning over materiality and the threat of death over the perpetuity of life processes. For an alternative I turn to bio-semiotics and cross-species scholarship around the question of the animal. Specifically, the paper asks what theories of waste would look like if instead of taking ‘dirt’ as their starting point, they began with trans-species encounters with animal scat. Following bio-semiotics and efforts to deconstruct the animal/human binary, it is suggested that the objectual forms commonly referred to as ‘waste’ are not arbitrarily classified but purposefully expended, and thus symptomatic of life’s spatio-temporal continuation. Waste matter, therefore, is best construed not as anthropocentric but as semi-biotic: a sign of the form of life to which it once belonged. This alternative perspective has implications for how approaches to industrial forms of mass waste can be reconceived.