Silage is rich, shredded plant matter that has been fermented in anaerobic conditions (that is, without contact with air). The resulting substance is exceptionally rich in a variety of acids, which are useful both for cow feed and for creation of biogas.
Silage is created by tightly packing the source material – Grass, Chaff or Hay – in impermeable plastic. This prevents the air from interacting with the material.
In game, this can be achieved in two different ways, depending on which source material is used:
Chaff and Grass are piled in massive bulks, over 100,000 liters in volume, within a concrete bunker at the Biogas Plant or the Cow Pasture. They are then compacted by driving heavy vehicles over them, and finally covered with a plastic blanket. Several game-hours later, the bunker is uncovered and is now full of Silage.
Round Bales of Hay can be wrapped individually in plastic strips, using a specialized machine. This turns the entire bale into Silage in less than a minute, but only processes one bale (4,000 liters) at a time.
The produced Silage can be sold directly at the Biogas Plant, by dumping it into a special receptacle. It fetches a very high price – higher than any other commodity in the game.