Green buildings: rice husk ash to cut greenhouse gas emission

Discovery News , July 7, 2009 reports a new way of processing rice husks for use in concrete, which could lead to a boom in green construction .

Rice husks form small cases around edible kernels of rice and are rich in silicon dioxide (SiO2), an essential ingredient in concrete. Scientists have recognized the potential value of rice husks as a building material for decades, but past attempts to burn it produced an ash highly contaminated with carbon, not useful as a cement substitute.

Every tonne of cement manufactured for use in concrete emits a tonne of the greenhouse gas carbon dioxide (CO2) into the atmosphere. Worldwide, cement production accounts for about 5 percent of all CO2 emissions related to human activity (http://dsc.discovery.com/convergence/globalwarming/timeline/timeline.html).

Rajan Vempati of ChK Group, Inc. in Plano, Texas and a team of researchers have figured out a way to make nearly carbon-free rice husk ash. Heating husks in a furnace drives off carbon, leaving fine particles of nearly pure silica behind. The process emits some CO2 but it is carbon neutral .

In recent years, concrete has become a repository for various waste products. blast furnace slag from steel plants, coal fly ash from power plants and silica fume, a leftover from the silicon metal industry, all have found application as replacements for Portland cement.

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