In this article, you will find a detailed review of the importance of rice and paddy as an energy resource in Turkey and around the world as well as the benefits of rice husk.
Paddy Husk (Husk) and Paddy Straw
Paddy cultivation and industry creates two major types of residues, the paddy straw and husk, which have a promising potential for energy. Although the rice husk use technology has been well-proven in industrialized countries in Europe and North America, it has not yet reached commercial scale in developing countries.
Rice husk is the most efficient agricultural residue in rice producing countries around the world. It is is one of the fundamental by-products of the paddy milling process, and makes for approximately 20 percent of total paddy weight. Rice husk, which mainly consists of cellulose and semi-cellulose, remains unused in many countries. Although rice husk has a great potential as an energy resource, it is still used as bed at poultry farms in Turkey. However, several facilities have started using it in the paddy drying systems.
Rice husk may also be used to generate energy by means of steam or gasification. As a small steam station is inefficient and a steam tank is difficult to maintain for small-scale energy production, the gasification method stands out. The gas produced from rice husk for diesel engine rice mills can be used with engines which run on dual fuel.
Rice husk technology has many benefits:
• It generates electricity and is a means of disposing of agricultural waste.
• Rice husk and straw can be used with other herbal bio-fuels in electricity production. However, the important thing here is the contamination, slagging and corrosion of the tank due to alkaline and chlorine components of the ash.
• Steam, which is a by-product of electricity production, can be used for paddy drying applications. Thus, the necessary drying process can be done at the parboiling rice facilities. This usage increases local income and decreases dependence on oil.
• Paddy husk can be used alone in burning or as a mixture with other bio-fuel materials. In this technology, burning tanks are used with steam turbines to generate electricity and heat.
• The energy of paddy straw is 14 MJ per kilogram with 10% humidity content. By-products are volatile ash and bottom ash which has an economical value and can be used in production of cement and/or bricks and construction of roads and fillings.
In many burning furnaces, it has been proven that steam fuels, which are designed for electricity production, are difficult to burn.
HEAT, GENERATED IN RICE HUSK FURNACE
The heat generated in rice husk furnace may partially replace the fossil fuels or heavy fuel consumption used for drying agricultural products.
This alternative has become the focus of energy development. As can be seen in the figure, several facilities have developed such systems. The heat generated by burning husk is used for drying the paddy. This helps to significantly decrease costs and prevent environmental pollution.
The ashes remaining from burning rice husk, which is a by-product of rice processing and drying facilities, can be used as a fertilizer or in cement and steel industries. This decreases the need for importing these materials.
The rice husk does not have any manufacturing costs for a rice mill. If it is considered as waste or garbage of the rice facility, this will become a huge burden for the rice mill. Rice husk should not be considered as fuel for furnaces.
THE SITUATION IN TURKEY
According to the data of Turkish Statistics Institution (TÜIK), Turkey produces 920 thousand metric tons of paddy. Paddy is also imported from abroad, but these number vary across years. Assuming the Turkey processes 1 million tons of paddy, it generates 20% of this amount as husk, which corresponds to 200 thousand tons. Considering the specific weight of paddy husk is 0,16 grams, you can estimate the area that is required for storage of this husk.
2.5 kg paddy husk = 1 liter diesel as thermal energy
If we assume that 200 thousand tons of husk is produced from 1 million tons of paddy processed in Turkey, you can use this dry 600 thousand tons of paddy. And if the total costs for this is 1 TRL/ton, then you can dry the whole paddy in Turkey for 600 thousand TRL. This is a considerable saving. Furthermore, 200 thousand tons of husk will generate 36 thousand tons of ash, which can be used as organic fertilizer.
Hopefully, Turkey will be adopting this technology in the near future.