(490f) Activated Sludge: A Potential Feedstock for Green Diesel

Green diesel is a renewable fuel produced from plant oils or animal fats either by hydrotreating or hydrocracking. In this study, the potential of producing green diesel from activated sludge was evaluated. Activated sludge obtained from a wastewater treatment plant in Tuscaloosa, AL was dewatered by centrifugation. Different extraction techniques, namely in situ transesterification, accelerated solvent extraction, and Bligh and Dyer method, were employed to maximize the lipid yield. Then, a series of analytical tools was utilized to characterize the extractable material from the activated sludge. Solid phase extraction using amino cartridge was done to separate the extracts into three fractions; neutral compounds, free fatty acids, and phospholipids. Preliminary results showed that, on the average, the extracts contain 49.2 % neutral compounds, 22.4 % free fatty acids, and 15.2 % phospholipids by weight. The three fractions were then analyzed for glycerides, free fatty acids and their ester equivalents, and metals using GC/FID, GC/MS, and ICP/MS, respectively. Initial results indicated that the neutral fraction consists primarily of C16:0, C16:1, C18:0, C18:1, and C18:2 fatty acids. The free fatty acids fraction on the other hand consists mainly of C16:0, C16:1, C18:0, and C18:1 free fatty acids. Based on the characterization data, pretreatment strategies/methods were developed to make the lipids from activated sludge a potential feedstock for green diesel production.