saturated moisture content, pellets were placed in the humidity chamber at 30C and 90% relative humidity for at least 48 h. The Meyer hardness of pellets was also measured by the MTI 50K press machine. The Meyer hardness (HM) was used to characterize the strength of single pellets with a flat surface [20,16].A pellet was laid horizontally between a mobile hemispherical probe and a fixed flat plate. The probe with a 6.35 mm diameter on the MTI 50 K press machine vertically moved downward at a speed of 1 mm/min to the pellet [15]. Both the force and displacement of the probe were recorded by the MTI 50 K press control system. The equation for calculating HM for pellet is given by [16]