Print 11 comment(s) - last by rmcdow.. on Jul 17 at 5:30 PM

Process could help to turn 80 million tons of trash into a valuable commodity

Rice is a staple crop of much of the world, but it's also a big waste generator.  On average 20 percent of rice by weight is discarded.  These dry, inedible husks are estimated to account for 80 million metric tons a year (out of a current annual rice yield of 422 million metric tons).

Tough and abrasive, the husks (also known as hulls) could only be used in low-cost materials such as fertilizer additives or bed soil.  But South Korean researchers think they've devised a way to cut down on the amount of agricultural waste from rice farming, by transforming the husks into a more expensive finished product.

A team at the Chungnam National University has extracted silica from the silicon-rich husks to convert into silicon for battery anodes.  

While nearly identical to sand from a molecular standpoint, rice silicon is deposited by the plant in porous nanolayers as a defense against insects and fungi.  That means that to extract the valuable material, researchers had to use a multi-step process involving acid and heat treatment.

Rice Hulls
Rice hulls can make great anodes, with a bit of TLC, it turns out [Image Source: Melvin Pereira]

However, the process appears to pay off, yielding high-grade electronics ready silicon.  The resulting yield is reportedly especially desirable for battery anodes due to its electrochemical characteristics.

The research team has published [abstract] their processing breakthrough in the prestigious peer-review journal, the Proceedings of the National Academy of Sciences (PNAS).

Sources: PNAS, Herald Sun News

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silicon from rice hulls
By rmcdow on 7/17/2013 5:30:57 PM , Rating: 2
I think many of the commenters here missed the point of extracting silicon from rice hulls. Silicon from glass is going to give you silicon boules, a solid silicon material that is good for making wafers, solar cells, etc., but has a small surface area, and therefore is not well suited for anodes of cells in batteries, as current battery technology is currently evolving toward. Finely divided silicon, which from what I can tell is being derived from the rice hulls, as it mentions the nano scale silicon, is going to have a large surface area for a given amount of silicon, and is therefore going to be well suited for the anode of a cell of a battery. The higher the surface area ratio to the amount of material used, the higher the capacity of the cell is going to be, in theory. Harnessing this surface area is another step in the development of the cells, but having silicon material that is already on the nanometer scale is a great place to start in developing a higher capacity cell for a battery.

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