Scum is an oil-rich waste from the wastewater treatment plants with a high-sulfur level. In this work, a novel process was developed to convert scum to high quality and low sulfur content biodiesel. A combination of solvent extraction and acid washing as pretreatment was developed to lower the sulfur content in the scum feedstock and hence improve biodiesel conversion yield and quality. Glycerin esterification was then employed to convert free fatty acids to glycerides. Moreover, a new distillation process integrating the traditional reflux distillation and adsorptive desulfurization was developed to further remove sulfur from the crude biodiesel. As a result, 70% of the filtered and dried scum was converted to biodiesel with sulfur content lower than 15 ppm. The fatty acid methyl ester profiles showed that the refined biodiesel from the new process exhibited a higher quality and better properties than that from traditional process reported in previous studies.
Bibliographical noteFunding Information:
This work was financially supported by grants from the Legislative-Citizen Commission on Minnesota Resources (LCCMR), MCES , University of Minnesota Center for Biorefining , the Natural Science Foundation of Higher Education Institutes of Anhui Province , China (Grant No. KJ2014A073 ) and Anhui Province Natural Sciences Foundation , China (Grant No. 1508085SQE213 ).
- Adsorptive desulfurization
- Solvent extraction