Apparatus and method for separating lightweight waste from product with cyclic pulses of air. An air separator includes a blower duct directing air upward through product conveyed on a foraminous conveyor. A pair of counter-rotating vanes in the blower duct cyclically open and close to establish a pulsating air flow in the center of the duct across the width of the conveyor. The pulsating air flow lifts lightweight waste from the product and blows it through a vertical duct above the conveyor to waste separation chambers for separation and disposal.