College of Food, Ag & Nat Res Sci
Scum is a rich source of recoverable energy, as it contains greases, vegetable and mineral oil, animal fats, waxes, soaps, food wastes, and plastic materials discharged from households, restaurants, and other animal product industries. The lipid content of scum can be as high as 60%. The energy store in scum, around 22.3 MJ/kg of dry scum, cannot be utilized if it is disposed of in landfills. Moreover, the disposal of scum increases operation costs in treatment plants. For instance, the Metro plant spends $200,000 a year just in transporting and landfilling scum. Therefore, there is an urgent need to develop a technology for energy recovery and beneficial reuse of scum.
These researchers are developing a novel technology that recovers energy and converts lipid, fatty acid, and soap in scum directly to biodiesel. The final product has a quality similar to ASTM-grade diesel. The researchers believe that by utilizing biodiesel derived from scum the wastewater treatment plant can: reduce cost of scum disposal to landfills; reduce petroleum fuel use and cost for fuel purchasing; and reduce GHG emissions by using biofuels. In addition, by diverting scum from landfills the technology could reduce methane emissions that have 25 times more global-warming potential as compared to CO2 in a 100-year's time horizon. All these benefits are likely to improve the economic and environmental sustainability of the wastewater treatment plant.
There are still uncertainties to the scum-to-diesel technology. In particular, the environmental performances of this technology have never been evaluated within current literature. When examining the technology, heat, electricity, and chemicals have to be provided for all conversion processes, which will raise environmental impacts, and thus, compromise the environmental benefits obtained in the production of biodiesel.