Optimization of granular waste production based on mechanical properties.

Pellet production of food and agricultural wastes is a suitable method to supply livestock feed. Mechanical properties of pellets play an important role in their handling and transportation. In this study, the mechanical properties of pellets made from waste are investigated. After the pelleting process, the pellets were dried with a laboratory convective hot air dryer until reaching a safe moisture content. The effects of feedstock moisture content (0.54, 0.88, and 1.2 kgw  kgDM -1 ), particle size (PS < 0.4, 0.4 < PS<1.2, and 1.2 < PS<2 mm), drying temperature (318, 333, and 348 K) and infrared radiation power of the dryer (0, 500, and 1000 W) on pellet durability, impact resistance, and compressive strength were investigated for two diets. The results showed that the mechanical properties of the pellets increased with decreasing particle size of the raw materials. The feedstock moisture content also affected the durability, impact resistant, and compressive strength of pellets. Moreover, mechanical properties were reduced considerably when the pellets were dried at a high temperature and infrared power. The diet with a lower fat content as well as a lower neutral detergent fiber indicated a higher pellet quality. Furthermore, the combination of raw materials and optimization of pelleting and drying conditions had a significant effect on the quality of the produced pellets.