Rice Husk Reinforcement in Polymer Composites

Rice

Rice or Oryza Sativa (as botanists prefer to call it) is not a tropical plant but is still associated with a wet, humid climate. It is generally believed that the domestication of rice began somewhere in the Asia. Rice is the world’s second largest cereal crop and produces the largest amount of crop residues. Rice, rice husk and rice straw are the main products of rice cultivation and processing (Binod et al., 2010). The average ratio of rice grain: rice husk: rice straw is 1:0.25:1.25 (Haefele et al., 2011).

The outermost layer of the paddy grain/rice is the rice husk, also called rice hull. It is separated from the brown rice in rice milling. Burning rice husk produced rice husk ash (RHA), if the burning process is incomplete carbonized rice husk (CRH) is produced. Globally, approximately 600 million tons of paddy is produced each year. On average 20% of the rice paddy is husk, giving an annual total production of 120 million tones. Paddy, on an average, consists of about 72 percent of rice, 5-8 percent of bran, and 20-22 percent of husk. Of all the plant residues, the ash of rice husk contains the highest proportion of silica.

Figure 1.

Rice

It is estimated that every ton of paddy produces about 0.20 tons of husk and every ton of husk produces about 0.18 to 0.20 tons of ash, depending on the variety, climatic conditions and geographical location.

Production Of Rice Over The World

The Table 1 shows the production of rice over the world particularly in China and India as there is huge production in comparison to rest of the countries.