Bench-scale production of sewage sludge derived-biodiesel (SSD-BD) and upgrade of its quality

Abstract Even if sewage sludge gain acceptance as a potential feedstock for biodiesel (BD) production, water content and contaminants in sewage sludge still remain as obstacles for the production and quality of biodiesel, respectively. Crude BD was produced from a feedstock of wet sewage sludge with 85% water content via in-situ wet-transesterification in a bench-scale (10 L) reactor, and then further treated for enhancing the BD quality to a transportation grade through a series of refining processes. The wet-transesterification was optimized in terms of crude BD yield by varying methanol dosage, methanol/co-solvent (xylene) ratio and reaction time. The maximum crude BD yield and the fatty acid methyl ester (FAME) content were 11.05 and 67.41%, respectively, when methanol dosage, methanol/co-solvent and reaction time were 15 mL/g, 0.5 and 12 h, respectively. The refining process consisting of vacuum distillation, degumming and neutralization, which satisfied the BD standards (EN14214) and visually improved color and transparency. Based on GC-FID analysis, the FAME content in the refined BD highly increased by eliminating the residual impurities. Applicability of the refined BD as a transportation fuel was confirmed by comparing the quality of the BD blended with the commercial petroleum-diesel (PD) at 3% (BD3) with the standard specification.