Innovative approaches are required to transition from a linear to a circular (bio)economy. Natural plastic alternatives, such as polyhydroxyalkanoates (PHAs), have great potential to promote this transition. In this study, we demonstrate the feasibility of converting solid waste animal fat (WAF) into the PHA copolymer poly(hydroxybutyrate-co-hydroxyhexanoate) (P(HB-co-HHx)) via bacterial fed-batch fermentation at 750-L pilot-scale using the engineered strain Cupriavidus necator Re2058/pCB113. A