Increasing CHP Productivity While Reducing Biosolids Volume and Climate Changing Gasses

This manuscript reports the first 30 months performance of POTW anaerobic digesters when feeding the pre-processed slurry produced from combining inedible kitchen grease (IKG) composed of fats, oils, and greases (FOG) with anaerobically digesting sewage solids to produce biogas for a combined heat and power (CHP) system. In 1993, the Millbrae facility began recording electronically solids processing data, such as the number of hauled loads, the wet ton weight of biosolids, polymer use relative to filter cake density/weight, electricity produced and bought, and digester stability. Comparison of these historical performance data with those of the first thirty months shows surprising results that yield benefits far greater than anticipated. These data indicate feeding pre-processed IKG into the Millbrae wastewater anaerobic digesters steadily and substantially increases the amounts of biogas produced, decreases the volume of biosolids disposed of by a sustainable 32%, improves the stability of digester operations, and improves biosolids dewaterability.