By-products
The main by-products of rice are rice straw, rice husk or hull, and rice bran.
- Rice strawis produced when harvesting paddy. Straw comes from what is left on the plant after it is harvested and the grains are threshed.
- Rice husks or hullsare generated during the first stage of rice milling, when rough rice or paddy rice is husked.
- Rice bran is produced during the second stage in milling, the whitening or polishing process, when the bran layer is removed from the brown rice kernel.
Rice straw
What is rice straw?
Rice straw is a rice by-product produced when harvesting paddy. Each kg of milled rice produced results in roughly 0.7–1.4 kg of rice straw depending on varieties, cutting-height of the stubbles, and moisture content during harvest. Rice straw is separated from the grains after the plants are threshed either manually, using stationary threshers or, more recently, by using combine harvesters (Figure 1).
Figure 1. Harvesting grain and straw using the combine harvester.
One hundred kilogram (100 kg) of paddy rice will generate approximately 5−10 kg of bran. Rice bran is a mixture of substances, including protein, fat, ash, and crude fiber. In many cases, bran contains tiny fractions of rice hull, which increases the ash content of bran. Bran composition is largely dependent on the milling process.
