Bangalore: Scientists at the Indian Institute Of Science (IISc) have been successful in extracting silica, used in industrial and pharmaceutical applications, from rice husk ash.

The process in which the silica is extracted is not only cost-effective, but also environment friendly, according to the scientists involved in the project.

Silica is normally generated from sand, which is extracted after a fusion of high temperature. This procedure requires energy and is investment intensive, scientists said.

India produces nearly 12 million tonnes of rice husk annually that contains about 80 per cent silica, which otherwise goes as waste.

"ISRO (Indian Space Research Organisation) had attempted a similar extraction method a few years ago. But ours is totally environment friendly and all the chemicals are regenerated," professor of department of aerospace engineering IISc and chief executive, advanced bio-residue energy technologies society (ABETS) Prof H S Mukunda said.

ABETS is working on installing a 20-tonne extraction plant at a unit in Andhra Pradesh, he said.

Japan, a rice-growing country, had shown interest in adopting the technology.

According to scientists, husk ash is mixed with caustic soda in a digestor, which generates sodium silicate.

Sodium silicate is then mixed with carbon dioxide gas to generate sodium bi- carbonate and silica, which is filtered and separated.

"Sodium bi-carbonate is processed with calcium hydroxide, which produces calcium carbonate and caustic soda. The caustic soda is recycled to be used in the digestor with the husk ash," scientists said.

This process also generates a small percentage of carbon, which can be activated with steam and used for water treatment plants, they said.

Whereas silica is used in pharmaceutical, cosmetics, reinforcing industry, salt and rubber industry, the other chemicals also find varied industry applications.

Prof Mukunda said if the husk ash were used on a large scale, it would be very economical to generate silica.

However, he said, economies of scale would also depend on many factors like location of the plant.

Prof Mukunda said plants with five to 20 tonne capacity can be installed near mega- power plants and co-generation plants and return on investment expected in around four years.

He said much of the rice husk generated in India goes as a waste, except for some use in brick and cement industry.

Prof Mukunda said the technology had potential in most of the rice growing countries in the world.

PTI