Physical, Chemical, and Rheological Properties of Rice Husks Treated by Composting Process

A composting treatment was employed in an effort to improve the processability of rice husks. Changes in the chemical composition, physical structure, and rheological properties of modified rice husks were analyzed. The results indicated that the average diameter of composttreated samples was significantly higher than that of the untreated samples because they were able to adhere to each other by the bacterial protein. Scanning electron microscopy images showed that the epidermis became rugged and lumpy because the composition of rice husks (cellulose, hemicellulose, lignin, and pectin) was partially decomposed, an effect confirmed by the chemical composition and FTIR analysis. Thermogravimetric analysis showed that the composted samples had better thermal stability than the untreated ones. Stress-strain curves showed that the treated samples displayed a moderately significant change of slope at about 0 to 10% strain, and they had better mechanical properties than untreated samples. Juxtaposing the rheological properties of both untreated and treated samples determined that the latter had higher apparent viscosity as a result of degradation and bacterial protein effects. All results indicated that the composting treatment changed the physical, chemical, and rheological properties of the rice husks, which are beneficial for its utilization and processability.