This study investigates the anaerobic co-digestion (ACD) of sewage sludge (SS) with fat, oil, and grease (FOG) and their saponified deposits, a common source of sewer blockage, aiming to improve biogas yield (BY) under realistic operating conditions. Three types of FOG: (1) olive oil (OO) representing monounsaturated fat, (2) sunflower oil (SO) representing polyunsaturated fat, and (3) pork fat (PF) representing saturated fat, and their saponified forms, were digested at various volatile solids (VS) addition rates (2%, 5%, 10%). BY increased by up to 47% with OO, but declined at higher rates of PF addition, and no effect on BY was observed at 10 % VS compared to the Control, indicating the potential inhibition of the AD process by larger rates of VS addition of fats containing poly and particularly saturated fats. Saponification significantly mitigated the inhibitory effects, especially for saturated fats like PF, by removing the lag compared to the Control at 10 % saponified PF VS and increasing BY by approximately 24 % relative to the Control. The results demonstrated the complex interactions and effects of different FOG and FOG deposits in SS ACD systems.