Silica Extraction from Biomass
Many plants contain silica. Agricultural products such as rice husks, contain as much as 10% silica by dry weight. The rice husk is the outermost layer of the rice grain, separated during the milling process. Around 20% of rice harvest weight is husk. In Asia alone, rice production produces about 770 million tons of husk annually.
Commercial rice mills process from 400 to 10,000 tonnes per day. The largest mills produce 2,000 tonnes of husk per day. This large biomass resource is available at little or no cost because rice husks have limited uses.
The use of rice husks include combustion for local electricity generation at smaller mills in Asia to pasteurisation and bagging for home gardening at larger mills in the USA. In many rice growing regions rice husks are sent to landfill or burned.
Precipitated silica, an amorphous form of silicon dioxide, is versatile product with many uses. For example, it is used as a filler, and a substitute for carbon black, in the manufacture of tyres and other rubber goods. It is also used in nutrition and health products, paints, inks and coatings, paper manufacture and toothpaste formulations. Precipitated silica is typically made from quartz sand via a sodium silicate intermediate product. It may also be made from the ash of silica containing plant materials. Both processes consume large amounts of energy and produce waste streams
New Energy Process for Silica Extraction
Leaf is researching and developing new low-energy processes for extracting silica from rice husks and other plant materials, especially agricultural by-products. Leaf aims for these processes to use much less energy than the conventional processes and produce very little waste. We are evaluating the biomass residue as a potential as a feedstock for the Glycell™ process.