How Do You Make Cheaper, Greener Silicon from Rice?

23 December 2015

A major breakthrough has been made in the process for manufacturing silicon. Not only does the new method use less energy (with potential cost savings of 90%), but it has a carbon footprint of almost zero and so has minimal environmental impact.

Since the 1930’s chemists have faced a ‘great challenge’ in how to manufacture silicon with less energy. Whilst the element silicon is readily available in all manner of organic substances, up till now scientists had been unable to efficiently uncouple the silicon from its tight bond with oxygen.

That is until Richard Laine, a professor of materials science and engineering at the University of Michigan discovered how it was possible. He is focusing his further studies on the readily available agrocultural waste of rice hull ash; the burnt remains of the shell that surrounds a grain of rice. As the University noted, “Laine found two easy and inexpensive ways to break that bond: ethylene glycol, or antifreeze, and ethanol, or grain alcohol. The antifreeze combined with a small amount of sodium hydroxide weakens the chemical bonds between the silica and rice hull ash at the beginning of the process, dissolving the silica into a liquid solution. The solution is then heated to 390 degrees Celsius, forming a polymer of silica and antifreeze.

Grain alcohol is then added at the end of the process. It’s chemically similar to antifreeze, so it easily swaps in to replace the antifreeze, which is then recycled. The liquid silica can then be distilled out of this second solution and used to make a high-purity precipitated silica product for industrial use.”

One of the most significant aspects of this discovery is that the basic raw material can be taken from any number of agricultural waste products, as silicon is abundant in most of them, but for now Laine plans to focus on processing rice hulls. Currently, thousands of tons of hulls produced every day are burnt for fuel, however many more thousands of tons are simply dumped as waste. This discovery may make this waste useable.

As a result of this research, Laine was awarded the 2015 Michigan Green Chemistry Governor’s Award and plans to turn his idea into a profitable enterprise. As Laine said whilst collecting his award, “I think eventually, we’ll be producing high-purity silica and other silicon compounds right next to the rice fields. By processing the rice husks we’ll be able to produce high-grade silica in a single location with little or no carbon footprint. It’s really very exciting.”

Questions still remain about the effectiveness of the up scaling and the quality of the mass product that will be produced, but as Laine explains, “If scale up is successful, the process will change the way high purity alkoxysilanes and precipitated and fumed silica are produced worldwide, because there are multiple sources of biogenic silicas everywhere.”

If successful, then clearly Laine’s company will benefit, but who else will? Would you be happy to trade or use a silicon made from rice hulls?