Pelletization of energy grasses: A study on the influence of process and material parameters on pellet quality

Pellets made from energy grasses, compared to high-volume pressed bales, provide higher energy density of the material and therefore reduce the cost not only in handling and transport, but also during storage. Three types of energy grasses commonly found in the area of the temperate belt - tall oat grass, black bent and hay as a natural grass ecosystem were investigated. The aim of this study was to determine the selected process parameters of pelletization and the mechanical-physical parameters of the produced pellets. Based on the combination of process (temperature and time) and the mechanical and physical (Durability, Hardness, Water resistance and Moisture) parameters of the pellets with statistical analyzes (Cluster Analysis, Principal Component Analysis), three stages of the pelletization process were defined and described - the initial, transient and stabilized phase. Specific process conditions for pelletization were determined for the production of quality pellets of selected energy grasses. Based on the results obtained and the statistical methods detailed in the article, the optimal process temperature interval for the pelletization of the assessed energy grasses ranges from 100 to 105 degrees C.