There is a reason why everything fried, fatty, and oily tastes so good to the human pallet. Fats and oils contain high amounts of energy (calories) per volume. This energy source is extremely easy for the body to access and use.
Similar to the human digestion system, the anaerobic digesters love Fats, Oils, and Grease (FOG). The microorganisms integral to the process thrive and multiply with ready access to FOG. This increased activity means more methane gas per volume of food waste. Other forms of food waste need to break down into simpler compounds before heading to the digesters, but the microorganisms can readily consume FOG.
Often restaurants hire a waste hauler to collect and dispose of their FOG separately than their other waste. Haulers truck in the FOG to WRR and empty it into one of three screened receiving bays. The filters strain any debris. Pressurize hot water breaks up clumps of fat or grease. Around 50,000 gallons of FOG can be accepted on a daily basis.
From the receiving bay, pipes carry the liquid food waste into the FOG holding tank. The tank’s capacity is 150,000 gallons. While all of the large tanks (FOG, Hydrolysis, and Digester) maintain a constant temperature, the FOG tank is insulated and slightly warmer in order to keep them in a liquid state.
Just like any animal’s gut, too much grease isn’t good for it, so FOG is added in proportioned amounts to the tank to create optimal conditions for the key bacteria growth.