The use of lipid sidestreams from food manufacturing has been overlooked as a feedstock for the production of single cell protein (SCP), which is a promising approach for the production of marine-free aquafeeds. While some studies have demonstrated that oleaginous yeasts can accumulate microbial lipids when cultivated with oils as a substrate, little to no work has been done to characterize the use of these organisms to convert waste oils to single cell protein. Here, surprisingly robust growth is shown by two oleaginous yeasts (Yarrowia lipolytica and Rhodosporidium toruloides) cultivated on waste lipids from industrial food processing. With final cell dry weight values higher than 40 g/L, strong productivity (3.3 g/L×Hr), and a remarkable conversion of substrate to biomass, these results demonstrate that waste lipids are a high energy feedstock for SCP production. This biomass is rich not only in protein, but also microbial lipids, with 25% lipid content that is more than 50% polyunsaturated fatty acids. While some work has investigated the ability of oleaginous yeasts to accumulate microbial lipids, the results here suggest a mixed method for production of both protein and lipids on such high energy feedstocks represents a promising alternative approach for generating high quality microbial aquafeed ingredients. Thus, this sidestream represents an attractive whole-cell ingredient for use as an aquafeed, or separate purified protein and lipids for food applications, without the need for genetic modification.