In tropical countries such as the Philippines, there are plenty of rice husks ... and also plenty of termites. A group of engineering students from the University of California, Riverside, recently decided to use the former to address the latter, by creating termite-resistant particleboard from rice husks.
Ordinarily, particleboard is made from wood chips that are bonded together using glue. Unfortunately, when used in building projects and otherwise, termites eat that wood – the same thing applies to plywood and bamboo.
On the other hand, rice husks contain silica, making them difficult for termites to consume. They're also a very abundant resource, often ending up being used as bedding for farm animals. It is estimated that a 4 x 8-foot (1.2 x 2.4-m) rice husk board would be worth about US$18, while traditional wood chip boards of the same size currently sell for around $25.
Another drawback of wood-based particleboard is the fact that the glue used in its production usually contains formaldehyde, which emits toxic gases. The students are currently using epoxy, which can also be harmful. They're looking into addressing the problem by replacing the epoxy with tannin from plants, or casein protein from milk.
So far, the tannin rice husk boards are sufficiently strong but not water-resistant, while the casein boards are water-resistant but not strong enough. Options include adding a waterproof coating to the boards, or increasing their strength by also including shrimp shells and/or rice straw with the husks.
Other possible or current applications for rice husks have encompassed using them as a source of silicon nanoparticles for use in batteries, an ingredient in "green" cement, a component of environmentally-friendly plastic, and a source of greenhouse gas-reducing biochar.
Source: UC Riverside
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