Rice ranks the first in the world food consumption followed by maize and wheat. In the world, there is 92 percent of rice grown in Asia. The major countries producing rice are China, India, Indonesia, Bangladesh and Vietnam. As a staple world food crop, the processing of rice results in two major agricultural wastes, namely rice straw and rice husks which are also called biomass residues. These two biomass residues can be used as a source of renewable energy, pellet fuel. In general, one ton of rice paddy can produce 290kg rice straw and 220kg rice husk which can produce 100kwh of power and 410~570kwh power, respectively.

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Rice Industry in the World

Rice is an important cereal in the human diet and second to wheat. As rice has more energy and nutrition than wheat, the consumption of rice increases fast in these years, which results that more plantation areas and the expanding of rice industry. China, India, Indonesia, Bangladesh, Vietnam, Thailand, Burma, Brazil, Japan and the United States are major producers of rice in the world, and the rice industries in these countries are growing quickly.
Recently, the rice industry receives more attention with the popular of biomass fuel. As a multibillion dollar industry, rice industry not only produces the food for human, but also produces biomass resources, rice husk (main byproduct from rice milling) and rice straw which can be used to make biomass pellets.
World Rice Production in 2010

Country Percent
China 28
India 19.7
Indonesia 9.5
USA 1.5
Others 40.4

Composition of Rice Straw and Rice Husk

Biomass Rice Straw (%) Rice husk (%)
Hemicellulose 35.7 28.6
Cellulose 32.0 28.6
Lignin 22.3 24.4
Extractive matter 10.0 18.4


How to Utilize Rice Industry Residues as Solid Fuel to a Large Extent?

In rice processing industry, rice husks are the main byproducts during rice refining.Therefore rice husks are a treasure for rice industry if they can utilize these biomass residues as solid fuel. As we all know rice straw and rice husks are loose and hard to handle, how to utilize them as solid fuel to a large extent? Pelletizing is the best way to convert these rice industry wastes into clean energy with high density, high calorific value.
Biomass pellets are a superior fuel compared with rice husk in energy dense and sustainable properties and convenience when use. Rice husk is low in density which causes transportation challenge. However, biomass pellets made from rice husk are in high density and uniform shape which make transportation easy. Compared with rice raw material, the combustion time are longer and the energy produced are more.

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How to Make Biomass Pellets from Rice Residues in Rice Industry?

High quality biomass pellets are dry, hard, and durable and more importantly , with low amounts of ash remaining after combustion. If the ash content of less than 1% after combustion, it can be called the premium pellets. when making biomass pellets, there are some factors should be considered carefully in order to make high quality pellets, such as moisture, pressure, and die diameter. The following are the steps for making biomass pellets form rice industry residues..
As the diameter of rice husk is about 2~3mm and the moisture low, dryer and grinder mill is not needed for rice husk pelletizing.
♦ Pelletizing: Use a rice husk pellet making machine to compress the rice husk/rice straw into a mass and then turn into pellets.
♦ Rice husk/ straw pellets cooling: Use a pellet cooler to cool the pellets as when the pellets leave the die, pellets are quite hot and soft. After cooled and dried, they become hard and durable.
♦ Pellets storage: you can build a storage bin for storing your pellets or use pellets packaging machine to bag them. Pellets should be stored in the cool and dry place. Keep them away from fire.