Cost-Effective Waste to Biodiesel Production at a Wastewater Treatment Plant

This report presents the results for the Cost Effective Waste to Biodiesel Production at a Wastewater Treatment Plant, a project conducted by the East Bay Municipal Utility District located in Oakland, California. The project will provide valuable input into the logistics of full-scale integration of fat, oil and grease waste receiving facilities and technical feasibility of biodiesel processes that fit into existing wastewater treatment plants.

The construction of a dedicated 60,000-gallon fat, oil and grease receiving facility at East Bay Municipal Utility District has demonstrated successful integration of a waste resource into the wastewater treatment process for renewable energy generation through anaerobic digestion and possibly future biodiesel production once the technology is ready for implementation.

In parallel, a bench-scale study was conducted to optimize the waste fats, oil and grease-to-biodiesel conversion processes and investigate sulfur removal methods for biodiesel made from brown grease. Bench testing demonstrated that a combination of silica gel adsorption and hydrogen peroxide oxidation desulfurization processes significantly reduced biodiesel sulfur by more than 90 percent at mild reaction conditions (ambient pressure and close to ambient temperature). The treated biodiesel met the American Society for Testing and Materials 6751 ultra-low sulfur standard of 15 ppm for several trials conducted, however not consistently. With the exception of not meeting the total sulfur limit, the brown grease biodiesel made by East Bay Municipal Utility District met all other Standard 6751 requirements. Further research is necessary to identify sulfur contaminant sources in the fats, oil and grease waste stream and to advance the biodiesel processing technology.

In addition, feasibility of converting alternate waste material, commonly found in wastewater treatment plant sewage streams, into biodiesel feedstock was investigated. Laboratory-scale tests were performed to harvest wax-like mycolic acids from Nocardia (a nuisance bacterium commonly found in the wastewater treatment process), and culture Corynebacterium glutamicum in wastewater for mycolic acid production to process as feedstock for biodiesel.