Comparison of Fiber Morphology and Chemical Compositions of Rice Straw Parts

Structural investigation of different parts of raw material is a step to achieve its more suitable processing. The aim of this study was to investigate fiber morphology and chemical composition of rice straw parts at different heights for internodes in lower, middle and upper parts, leaves and nodes separately as wella their mixture. Fibers were separated using Franklin method and their chemical composition was determined according to the related TAPPI test methods. Results showed that fiber length, fiber diameter and cell wall thickness of fiber decreased in internodes from down to top. The largest diameter and cell wall thickness were related to the nodes. The amounts of ash, acetone extractable materials, lignin and cellulose of leaf were higher than the other parts of the straw. Ash and acetone extractable materials percentage increased in straw from down to top but amounts of lignin and cellulose decreased in straw in the same direction. The results indicate that the internodes of rice straw are better than the leaves for pulping because of the average longer fibers and lower percentage of extractive, ash and lignin in internodes than the levels. So, in preparation of the pulp raw materials, it is necessary to remove the unsuitable parts of rice straw such as leaves and nodes.