A novel process was developed for converting scum, a waste material from wastewater treatment facilities, to biodiesel. Scum is an oily waste that was skimmed from the surface of primary and secondary settling tanks in wastewater treatment plants. Currently scum is treated either by anaerobic digestion or landfilling which raised several environmental issues. The newly developed process used a six-step method to convert scum to biodiesel, a higher value product. A combination of acid washing and acid catalyzed esterification was developed to remove soap and impurities while converting free fatty acids to methyl esters. A glycerol washing was used to facilitate the separation of biodiesel and glycerin after base catalyzed transesterification. As a result, 70% of dried and filtered scum was converted to biodiesel which is equivalent to about 134,000 gallon biodiesel per year for the Saint Paul waste water treatment plant in Minnesota.
Bibliographical noteFunding Information:
The authors are grateful to Adam W. Sealock, Larry Rogacki, and Jason Willett of the Saint Paul Metropolitan Council Environmental Services (MCES) for providing financial support and helping with the scum sample collection. We would also like to thank our graduate student Nonso Onuma for preparing the samples. This project is supported by grants from the Legislative-Citizen Commission on Minnesota Resources (LCCMR) and MCES.
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- Acid washing
- Glycerol washing
- Wastewater treatment plant