ABSTRACT
Processing rice straw and husks as co-products Nguyen Van Hung, Carlito Balingbing, James Quilty, Bjoern Ole Sander, Matty Demont and Martin Gummert, International Rice Research Institute (IRRI), The Philippines
1 Introduction: rice by-products
2 Availability of rice straw and husks
3 In-field rice residue processing and management
4 Off-field rice residue processing and management
5 Using rice residues for energy production
6 Non-energy uses of rice residues
7 Summary
8 Future trends
9 Where to look for further information
10 References
Each kilogram of milled rice produced results in roughly 1.4 kg of rice straw, 0.28 kg of husk and 0.15 kg of rice bran as by-products from rice production during harvesting and milling. Rice straw is separated from the grains when the plant is threshed either manually or mechanically using stationary threshers or combine harvester, while rice husk is a by-product produced during milling. Rice bran, also a by-product of milling, which has multiple established uses as animal feedstock and in the food and cosmetics industries, is not discussed further in the chapter. One of the most important differences between the by-products, rice straw and rice husk, is the location of their production within the rice value chain. Rice husk is produced at a centralized location (the rice mill) and is relatively uniform in moisture content, composition and particle size. Rice straw is produced at the point of threshing, which, where manual threshing or stationary threshers are used, is a central point within the field, or where combine harvesters operate the straw is distributed across the harvested field. In addition to being an uncentralized source of biomass, the moisture content (MC), composition, and particle size of rice straw vary greatly depending on a range of environmental and management variables. Open-field burning has always
been an option for rice farmers, but was not practised much in traditional rice production systems.
