ricehusk

Rice husk, also called rice hull, is the tough outer covering of the rice grain (the caryopsis). It is removed during milling to produce white or brown rice and is collected as a major byproduct of rice processing. The husk is fibrous, lightweight, and rich in silica, and it remains distinct from the bran layer that is removed to produce brown rice.

Composition and properties: The husk consists largely of silica, along with cellulose, lignin, and minor minerals. Silica in the husk becomes rice husk ash (RHA) when burned. The material is hollow and porous, with relatively high ash content. The exact composition varies depending on rice variety, growing conditions, and milling methods.

Production and yield: Rough rice typically yields about 20% to 25% husk by weight, though figures vary by cultivar and processing. The husk is separated from the grain during dehulling and is often handled as a separate byproduct.

Uses: Rice husk is a versatile byproduct. It is used as a renewable fuel in some rice mills and power plants. Its ash, known as RHA, is used as a pozzolanic material in cement and concrete, as a soil amendment, and as an adsorbent for certain contaminants. It can be processed into silica or activated carbon, and it is used in lightweight building materials, insulation, animal bedding, and composting applications.

Environmental aspects: Proper utilization of rice husk reduces waste and emissions associated with disposal or open burning. Advances in processing and materials applications help turn this byproduct into valuable resources in rice-based economies.