The energy life cycle assessment for the production of biodiesel from rendered lipids in the United States is presented in this study. Three different scenarios were found eligible for analysis: (1) conversion to biodiesel, (II) rendering and conversion, and (III) farming, rendering, and conversion. The amounts of energy required in farming, meat processing, and baseline conversion to biodiesel were reviewed front the literature. The thermal energy and electricity Used in rendering were surveyed front the U.S. rendering industry. For animal fats, scenario III resulted in a net energy ratio (NER, ratio of energy outputs to energy inputs) much lower than I. In contrast, the NERs for scenarios I and If were both found to be > 1. For scenario I, the NER was found to be >3.6, larger than the value typically reported for soybean oil (SBO) biodiesel. As for the waste SBO grease, the NER Was found to be > 1 for both applicable scenarios (I and II). To a limited extent, sensitivity analysis was used to evaluate changes in assumptions with respect to the type of fuels employed in the generation of thermal energy as well as the method for biodiesel production.