From the article:
Rice husk is an agricultural residue abundantly available in rice producing countries like India, China, Brazil, and South East Asia. Rice husk is mainly used as a fuel in industries in boilers for process energy requirements and for power generation. Rice husk is a fuel having high ash content, varying from 20 – 25 % of rice husk, the major constituent (>90 of ash) being silica. This ash has some limited use as a heat insulator in steel rolling mills, in brick making and in cement manufacturing, but largely remains unused. Due to the low bulk density of the ash (around 200 kg/m3 ) its disposal in large volumes creates environmental problems.
The patented Indian Institute of Science Precipitated Silica Technology (IPSIT) developed at CGPL, IISc, Bangalore is a novel method of extracting precipitated silica in commercially viable way from rice husk ash. Precipitated silica finds application in many of the industries like from tyre industry, food industry, paint industry, cosmetics etc and is used as reinforcing agent in rubber, thickening agent in paints, anti caking agent in food industry. These applications require silica of different grades which are characterized by surface area, tapped density, oil adsorption capacity, silica content etc. The IPSIT process is able to meet the different industry demands with respect to the quality of the silica. The investment cost for 5 TPD precipitated silica production by this process is around 1.6 million USD and the production cost is roughly 0.6 US. The selling cost is around 1 USD.