Abstract
Densified rice straw can be easily handled, which may reduce transportation and storage costs. The influence of densification parameters on the quality properties of rice straw pellets was the main focus of this study. The conditioning factors analyzed were: moisture content of the feeding material (12%, 15% and 17%), starch as an additive (0%, 1% and 2%), operating temperature (below and over 50°C), and the influence of three flat dies with different diameter/compression length (6/20, 6/24 and 8/32mm/mm) on the pellet properties (durability, hardness, moisture content, dimension, and single and bulk densities). The quality of the pellets was evaluated in view of current standards. The results showed that the studied feeding and operating conditions had significant effects on the pellet properties, especially durability and bulk density, which are the most important parameters for pellet quality. All dimensions, most bulk densities, and few durability values of the produced pellets achieved the standard limits. The highest pellet quality, with durability 99.31%, was obtained with operating conditions 2% starch ratio, 17% feeding moisture content, temperature<50°C and die size 8/32mm/mm.
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•Durability and bulk density were the most indicative parameters for rice straw pellet quality.•Hardness and pellet density were positively correlated with durability and bulk density, respectively.•The highest pellet quality produced at 8/32 die size, 2% starch additive, 17% feeding moisture content, and temperature lower than 50°C.