Integrated 
sewage or digestible wastes, and fats, oils, greases and waxes (
FOG) 
waste treatment methods, systems and facilities include a 
slipstream loop incorporating circulation pumps, hot water heat exchangers and conventional anaerobic digesters for continuously circulating actively digesting 
sludge at a rate to preclude 
solid settlement accumulation as a warm flowable 
slurry source. The warmed actively digesting 
sludge is pumped from the 
slipstream loop through a rock trap into a delivery / input loop both for aiding transport or delivery of 
FOG waste to, and for partially filing a closed receiving / conditioning 
holding tank, where the warmed actively digesting 
sludge softens and liquefies the 
FOG wastes offloaded into the 
holding tank for further treatment at a desired treatment temperature range (whether psychrophilic, mesophilic, or thermophilic). The contents of the closed receiving / conditioning 
holding tank are continuously mixed by a bottom-top recirculation 
chopper pump to pre-treat the FOG wastes, liquefying and decreasing solids particle size allowing acidogens in the actively digesting sludge to pre-digest such wastes producing 
volatile fatty acids, some 
biogas and a highly bioreactive, flowable feedstock 
slurry. The produced highly bioreactive, flowable feedstock 
slurry can then injected back into the actively digesting sludge 
slipstream loop at a controlled rate where the 
resultant mixture then is introduced, together with raw 
sewage or other digestible wastes, into input or head ends of 
waste treatment systems having anaerobic digesters for 
digestion of solids and steady-state 
methane production. Advantages of the integrated 
system relate to a partial 
digestion of the FOG in the reaction / holding tank generating 
volatile fatty acids that suppress expression of 
methane producing methagens in the holding tank, increased steady-state 
methane production and significantly reduced solids volume of treated digestible wastes (
sewage) and FOG wastes.