Biodiesel and other renewable fuels are of interest due to their impact on energy supplies as well as their potential for carbon emissions reductions. Waste animal fats from meat processing facilities, which would otherwise be sent to landfill, have been proposed as a feedstock for biodiesel production. Emissions from biodiesel fuels derived from vegetable oils have undergone intense study, but there remains a lack of data describing the emissions implications of using animal fats as a biodiesel feedstock. In this study, emissions of NOx, unburned hydrocarbons and particulate matter from a compression ignition engine were examined. The particulate matter emissions were characterized using gravimetric analysis, elemental carbon analysis and transmission electron microscopy. The emissions from an animal fat derived B20 blend were compared to those from petroleum diesel and a soy derived B20 blend. No statistically significant differences were observed between the fuels in the gaseous emissions. Notable differences in engine-out particulate matter emissions characteristics were observed between the B20 blends and the petroleum diesel, but few differences were observed between the B20 blends using animal fat based biodiesel and those using soy based biodiesel. Given very similar engine-out particulate matter and gaseous emissions compositions for animal fat and soy B20 blends, it is suggested that diesel exhaust aftertreatment systems designed to operate with soy biodiesel blends are likely also compatible with animal fat derived biodiesel fuel blends.