Comparison of the Lipid Content and Biodiesel Production from Municipal Sludge Using Three Extraction Methods

Abstract

In light of the rapid development of society, wastewater treatment ratios and amounts as well as the amount of sewage sludge production have increased. High water content, heavy metal, and viral content of sewage sludge have resulted in a serious environmental problem. In this study, the performances of acid hydrolysis extraction, Soxhlet extraction, and the water bath shaking method were compared in terms of lipid extraction from sewage sludge. These methods are more cost-effective and easier to apply compared to supercritical extraction. The effects of different organic solvents, including ether, hexane, acetone, chloroform–methanol, and solvent combinations, on the extraction rate were also studied. More polar lipids were extracted by polar solvents (6.4%) than by nonpolar solvents (3.4%) from mixed sewage sludge. Soxhlet extraction, which extracted 2.5–10.3% lipids from dried sewage sludge, performed considerably better than acid hydrolysis extraction (2.2–7.5%) and the water bath shaking method (3.0–...