Rice Hulls as a Renewable Complex Material Resource

As a result of rice grain processing, a big amount of waste (up to 20%) is produced. It is mainly rice hulls. The main components of rice hulls are cellulose, lignin and mineral ash. The mineral ash quantity in rice hulls varies from 15 up to 20%, by weight of the rice hulls. The mineral ash consists of amorphous silica (opal-type). Due to the high content of silica in rice hulls, the material burns with difficulty under natural conditions, and it is biodegradably destroyed only with difficulty, when composted. Utilization of rice hulls then becomes an ecological problem due to huge rice production and its continuous growth. At the same time, the annual quantity of silica content in rice hulls is comparable with the quantity of amorphous silica produced as a mineral resource. The issue of manufacturing cellular glass silica construction materials from rice hulls as a renewable resource is discussed in this paper. The utilization technology is based on an amorphous silicon oxide with the use of energy from the combustion of the organic component of rice hulls.