The Sewer (formerly known as "Sewage Collector") will examine a 1x1 area (expandable with upgrades) above them, and very slowly generate Sewage, based on the number and size of animals within the Sewer's operation area. Large animals will produce more Sewage. If another Sewer is detected within the collection radius, the Sewer will jam and stop working for 40–80 seconds (there is no indication of this in the GUI). This machine does not require power. Note that the recipe may not be the same depending on which version of FTB you are running. To be sure, search for it in your inventory. The sewer will also generate Mob Essence from XP drops, each point of experience will generate 66mb of mob essence. Ideal to combine with a Melee Turtle.
Thermal Expansion Recipe