Rice Hulls

Abstract

According to the statistics supplied by the IRRI (1988), the world's paddy rice (Oryza sativa) production in 1987 was 470 million MT. Most of this tonnage is produced in Southeast Asia. A major derivative of the rice crop is the hull, a fibrous, nondigestible commodity representing some 20{%} of the dried paddy on-stalk (Yoshida 1981). Dried paddy on-stalk yields 52 wt{%} of white rice, 20{%} hull, 15{%} stalk, and 10{%} bran. The remaining 3{%} is lost in the conversion process. If all the paddy rice available were commercially milled, 98 million MT of hulls would have been produced in 1987. Because of their abrasive character, poor nutritive value, low bulk density, and high ash content, only a small percentage of the hulls can be disposed of for certain low-value applications such as chicken litter, juice-pressing aids, and animal roughage. If not properly utilized, rice hulls will create a growing problem of space and pollution in the environment. In some countries, rice hulls and straw are used as fuel in parboiling paddy rice. It is likely that hull utilization will increase in light of the high cost of fuel and the energy crisis confronting the world population.