Grease trap waste and sewage scum grease are underutilized, high-lipid waste streams that have the potential to be converted into biodiesel. This report presents results from a longitudinal study of the variability in waste grease composition, a demonstration of technical feasibility of production of biodiesel from these wastewater greases, and an evaluation of the environmental and cost tradeoffs using life cycle assessment and techno-economic analysis. The average lipid content of sewage scum grease is seasonally dependent; lipid content ranges between 15-40% in cooler months and 3-21% in warmer months. The lipid content of grease trap waste ranges between 1-25% with no apparent seasonal trend; however grease trap waste is easily partially-dewatered by gravity separation to a lipid... content of 11-100%. Lipids extracted from wastewater greases have high acidity, a high fraction of saturated fatty acids, and a high concentration of impurities. Biodiesel produced from these waste greases meets all fuel specifications except for sulfur content. Separating lipids from wastewater greases, converting the lipids to biodiesel, and substituting biodiesel for low sulfur diesel produces a significant reduction in greenhouse gas emissions.