An apparatus for processing a sample including fibers and trash, having a cylinder rotating in a first direction for receiving the sample. The cylinder has a surface with rigid pins. The pins engage and retain the fibers of the sample. A collection surface receives the trash that falls from the cylinder. A counter-flow of air moves in a separation region between the cylinder and the collection surface in a direction that is substantially perpendicular to and towards the underside of the cylinder. The counter-flow of air has at each position within the separation region an air-flow velocity that is sufficient for the counter-flow of air to blow the fibers that are not originally retained by the pins up toward the cylinder and thereby engaging the fibers with the cylinder, and yet insufficient to prevent gravity from pulling the trash downward through the counter-flow of air.