Rice and Husks
20% - it’s the percentage of husk contained in rice (average).
In 2012, about 738.1 million tonnes of rice was produced worldwide (FAOSTAT: Production-Crops, 2012 data).
If you do the math to figure out how many tonnes of rice husk were separated from the grain of rice during the milling process you will see that it is an abundant resource.
What’s more is that the production of rice is growing and thereby rice husks too.
Which are the concerned countries?
China,India, Indonesia, Bangladesh, Vietnam, Thailand, Philippines, Myanmar, Braziland Japan are the ten biggest producers of rice. They are not the only countries producing rice though, the African continent also hosts rice producers like Niger, Chad, Cameroon…
What is rice husk used for?Centuries ago, it was used to clean teeth in India up until toothpaste appeared. But mostly, it was just treated as waste. For example, “In Vietnam, it used to be a waste some years ago and was dumped in the rivers, causing a big problem, but now it has a value,” Mr. Gummert said.
Today, people use it to brew beer, and for fireworks, pillow stuffing and more. As you may have guessed, rice husk is also linked to cookstoves. Indeed, special cooking devices have been designed to use rice husk, the rice husk stove. Let’s take again the example of Vietnam. There, traditional stove models are mostly gasifiers (i.e. rice husk stoves). Considering the heaps of rice husk available, the idea to design this kind of stove was just logical.
Why stoves are specially designed for rice husk?
If you try to burn rice husk with traditional improved cookstoves, it doesn’t work. Indeed, it’s required to strike a balance compacting the rice husk. If the heap is too compact, the air can’t access the inside chamber and if it’s too widely dispersed, it doesn’t burn. That’s why special stoves have been designed. One of the most common includes 2 chambers. The internal chamber is used to stock the rice husk to which we set fire. This releases gases from the burning rice husk which goes to the second chamber and these gases then go out from the top of the stove and are burnt to produce flames.
You can find a technical fact sheet here: http://answers.practicalaction.org/our-resources/item/stoves-for-rice-husk-and-other-fine-residues
What’s the difference between a rice husk stove and an ICS?
They are two different technologies and each stove design is adapted to different fuels. Basically, biomass cookstoves can’t burn rice husk and gasifiers can’t burn wood or charcoal.
Common gasifiers are not very efficient, but their advantage is that they emit less particulate matter (PM) and carbon monoxide (CO), while biomass cookstoves are efficient but release more PM and CO.
Also, gasifiers are being improved and you can find some with which you can use other fuels (e.g. pellets).
As you can imagine, using this technology remains more complicated than using biomass cookstoves, as seen in Cambodia for example.