3. Wheat and Rice Straw Fibers

Wheat is the fourth most popular crop in the world with a production of 675 million tons in 2012. About 1–1.2 tons of straw are generated per acre and wheat straw accounts for about 50 % by weight of the cereal produced. Straw is mainly used as animal fodder and bedding, for thatching, and for artistic works, and in many countries, wheat straw is burnt to prevent soilborne diseases. Extensive studies have been done to understand the potential of using wheat straw for pulp and paper production. However, wheat straw has a waxy covering on the surface and a unique morphological structure that makes it difficult for alkali to penetrate into the straw and separate fiber bundles with the length, fineness, and tensile properties required for textile and other high-value fibrous applications. As seen in Fig. 3.1, the individual cells or ultimate fibers in wheat straw have serrated edges that get interlocked with each other. It was found that a pretreatment with detergent and mechanical separation with steel balls were necessary before the alkaline treatment to obtain fiber bundles from wheat straw [07Red]. Fiber bundles obtained from wheat straw had tensile properties similar to kenaf as seen in Table 3.1. About 20 % fibers were obtained, but the fiber bundles obtained were considerably coarser than cotton and linen.