All batches of AP were pelleted on the laboratory flat die pellet press (model 14-175, AMANDUS KAHL GmbH & Co. KG, Germany), equipped with a 18 mm thick die, having a 6 mm opening diameter (L/D - 1:3). Material throughput was 15 kg/h in all pelleting treatments. Specific energy consumption of pellet press (kWh/t) was calculated by using the following equation: