Utilization of Rice Husk and Their Ash: A Review

Due to rapid growth in population and industrialization, some new technologies are made for waste utilization and cost reduction in industrial processing by using rice husk (lignocellulosic biomass) as a valued material. In this paper various industrial and domestic application of rice husk and rice husk ash are discussed. Rice husk act as adsorbent for removing heavy metals from wastewater. In mostly countries of the world, lignocellulosic biomass used for bioethanol production because it is a renewable and environment friendly fuel. With the review, it is hope that researchers concentrate on producing non-food feedstocks. KeywordsLignocellulosic Biomass, Rice husk, bioethanol Received 07/11/2013 Accepted 10/12/2013 © 2013 AELS, India INTRODUCTION Rice is an important staple food for approximately half of the world population [1]. More than seventy countries mainly China, India, Indonesia produce rice. Rice husk is one of the most widely available agricultural wastes in many rice producing countries of the world. Rice hulls (or rice husks) are the hard protecting coverings of grains of rice and removed from rice seed as a by-product during the milling process. Rice husk used as a valued added raw material for different purposes. It possess various properties that make them suitable for bioethanol production [2]. Rice husk biomass is made up of three polymers like cellulose, hemicelluloses and lignin. Rice husk like other lignocellulosic biomass feedstock has been explored as the cheapest feedstock for bio-ethanol production. It is essentially free as waste product from agriculture sector and forest residues. Utilization of these wastes could solve the disposal problem and reduce the cost of waste treatment [2]. When rice husk incinerated, ash is obtained called rice husk ash [3]. In this review, we are discussing about different applications of rice husk and rice husk ash. Rice hulls that are parboiled (PBH) are used as a substrate or medium for gardening, including certain hydrocultures [4]. It has been shown that rice hulls do not affect plant growth regulation [5]. Rice hulls are used as pillow stuffing. The pillows are loosely stuffed and considered therapeutic as they retain the shape of the head. COMPOSITION OF RICE HUSK Rice husk contains 75-90 % organic matter such as cellulose, lignin etc. and rest mineral components such as silica, alkalis and trace elements [6]. Rice husk is unusually high in ash compared to other biomass fuels in the range 10-20%. The ash is 87-97% silica, highly porous and lightweight, with a very high external surface area. Presence of high amount of silica makes it a valuable material for use in industrial application [7]. Other constituents of Rice Husk Ash (RHA), such as K2O, Al2O3, CaO, MgO, Na2O, Fe2O3 are available in less than 1 %. Rice husk having bulk density of 96-160kg/m3 , oxygen 31-37%, nitrogen 0.230.32%, sulphur 0.04-0.08%. UTILIZATION OF RICE HUSK Rice husk used for different applications depending upon their physical and chemical properties like ash content, silica content etc. In power plants, rice husk is directly used as a good fuel. It is also used as a raw material for making some compounds like silica and silicon compounds. Rice husk have various application in different industries and domestic fields. a) As an industrial fuel Research Journal of Chemical and Environmental Sciences Res. J. Chem. Env. Sci., Volume 1 Issue 5 December 2013: 126-129 Online ISSN 2321-1040 CODEN: RJCEA2 [CAS, USA] Available Online http://www.aelsindia.com ©2013 AELS, India