Process development for scum to biodiesel conversion

• It is the first time that scum was utilized and converted to produce liquid fuel.
• Technical aporia have been solved including impurity and layer difficulty.
• 70% dried and filter scum could be converted to biodiesel.
• Designed process is highly scalable and has great commercialization potential.
• Not only bring revenue to the wastewater plant but reduce waste and pollution.

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.