If yellow grease is used as feedstock for biodiesel production, how much feedstock (kg) is needed to make one gallon of biodiesel? assume that yellow grease is consisted (by weight) of 15% free fatty acids (ffa), 5% water, 0.5% insoluble solid, and the rest as triglycerides and both ffas and triglycerides are utilized for biodiesel production. use oleic acid for ffa and oleic acid methyl ester for biodiesel.]