Crop residues , the alternate raw materials of tomorrow for the preparation of composite board ”

The rapidly changing economic and environmental needs of society are putting everincreasing pressures on the forest industry to “do more with less”. In practical terms this means, increasing the conversion and efficient use of wood fibre resources, producing more fibre on a shrinking land base, using environmentally friendly processes and technologies considering the use of non-wood ligno-cellulosic fibres for industrial products. One of the ways the forest industry has responded to the global challenges in fibre utilization and processing efficiency was through the accelerated development of composites. A new environmentally friendly technology for turning agricultural residues like bamboo, rice husk, jute, coconut coirs, bagasse. wheat straw, chir pine needles, cotton stalks, casuarina leaves, banana stem etc., into quality value-added composite products using conventional formaldehyde-based resins have been developed. The new technology highly favours environmental protection and sustainable development by recovering and re-utilizing organic wastes such as crop residue. Adoption of these technologies also leads to Implementation of a green solution as an alternative to crop residues being burnt and disposed into soil. Composites from crop residues eliminates the release of carbon from decaying crop residues into air, which contributes to the global warming through greenhouse effect and also decreases the constantly growing pressure over the forests for wood resources. The crop residues were not being utilized earlier for board production with the use of conventional formaldehyde based resins due to its fibre cells being surrounded by a layer of wax/silica. This layer prevents the water based formaldehyde resins which are widely used today in all plywood industries from forming a sufficiently strong bond between the fibres. However, the new technology enables the destruction of the wax/silica layer by using mechanical high shear forces accompanied by a thermal and chemical treatment. This combined chemi-thermo-mechanical process allows the formaldehyde resins to penetrate and adhere the individual fibres. The panel products produced meets the requirement of strength properties as per the relevant specifications. Introduction With dwindling wood resources on one hand and increasing demand for the wood based panel products on the other, attention is gaining momentum on the utilization of agro-residues and also recycling of wood waste for manufacture of panel products. Unlike plywood, Particle Board (PB) and Medium Density Fibre Board (MDF) provide enough scope for the substitution of wood by non-wood fibre resources. However growth of PB and MDF industry in India has been sluggish compared to world trend in this field because of high production cost, high cost of petroleum-based resin adhesives and resistance by the carpenters who have been playing key role in shaping the consumer acceptance with this material. The PB production in India was started in 1950 and as on date there are approximately 14 units working. Out of these, two units which have started production of PB and prelaminated PB and marketing their products under the trade name “Eco Board” is totally based on sugarcane bagasse raw material. Both the units are situated in Maharashtra State and set up with imported machinery. One at Jambhulwadi in Sangli district which has the production capacity of 15 lakhs sq. mtrs. Per annum and onother unit at Velapur in Solapur district which has the production capacity of 26 lakhs sq. mtrs. Per annum. PB production has largely remained wood based despite availability of non-wood raw materials whose stability to produce PB conforming to Indian standards specification, has been thoroughly investigated at the Institute, for example, Rice Husk Particle Board, Pine Needle Particle Board, etc. some of these products have been demonstrated at the pilot scale level and commercialized. However, the greatest obstacles to increase the utilization of non-wood fibre/utilization of agro –residues are difficult in collection and storage of raw material is available in sufficient quantity but not used due to problems associated with technical intractability or alternate use considerations or both. However, the appetite of the construction industry for structural wood products continued to grow. Thus, the 1970s and 1980s witnessed the rapid development of structural wood composites, both panels and lumber substitutes The rapid evolution and manufacture of these wood composites would not have been possible without high performance synthetic adhesives. Indeed the wood composites and adhesives industries developed a profitable interdependence. Even in India , with its huge forest resource, there is increased demand and competition for wood residues by the paper industry and the rapidly growing composites industry. This makes the use of alternative fibre such as agricultural/crop residues more attractive and feasible. In addition, the move to find substitutes for solid wood has been stimulated by factors, such as diminishing resource quality, rising timber prices, and growing world demand for wood products. Composites are an attractive application for these materials because their manufacturing processes are highly automated and adaptable to various types and forms of raw material. The paper and wood-based panels industries make use of forest wood as a raw material for their products. The use of other renewable resources such as agricultural residues (wheat straw, rice straw, etc.) in the production of composite panels (i.e. particleboards, fibreboards) and paper products has recently been considered attractive both from the economical and environmental point of view. The use of straw can by this way help to protect the virgin forests in regions where there is a shortage of wood. In addition, great quantities of straw residues are available today in other parts of the world where the burning of straw has been prohibited, and no proper (efficient) uses for these wastes have been found up to day. An innovative environmentally friendly process for turning agricultural residues (agriwaste) into quality boards suitable for use in the furniture and construction industries has been developed POTENTIAL FOR USE IN COMPOSITEPRODUCTS In India, grain and other seeds are the main objectives of the farming activity, there is great interest in developing uses for residues that are currently burned or ploughed back into the ground. Most of the developing countries are very rich in agricultural and natural fibre. Except a few exceptions, a large part of agricultural waste is being used as fuel. India alone produces more than 400 million tonnes of agricultural waste annually. It has got a very large percentage of the total world production of rice husk, jute, stalk, baggase and coconut fibre. All these natural fibres have excellent physical and mechanical properties and can be utilised more effectively in the development of composite materials for various building applications. The quantity of these materials available are shown in Table I From centuries, mankind has used natural fibre for various types of application including building materials. In most of the countries, users have explored the possibilities of using natural fibre from different plants, which includes bagasse, cereal straw, corn stalk, cotton stalk, kenaf, rice husk/rice straw etc. Most of the fibre were used mainly for the production of hard board and particle board. Emergence of polymers in the beginning of the 19th century has provided the researcher new dimensions to use natural fibre in more diversified fields. At the same time, necessity has also increased the interest in synthetic fibre like glass fibre which, due to its superior dimensional and other properties seems to be gaining popularity and slowly replacing natural fibre in different applications. As a result of this change in the raw material and production process of synthetic fibre based composites, energy consumption has increased. The environmental loss suffered by society due to pollution generation during the production and recycling of these synthetic based materials has once again drawn attention to the use of natural fibre. The renewed interest resulted in new ways of natural fibre modifications/use and brought it to be at par/superior to synthetic fibres. Now it is in use from making rope to spacecraft applications and the building industry has also come up as one of its main beneficiaries. Table I AGRO & FOREST RESIDUES AVAILIABLE IN INDIA No Particulars Tonnes/ annum (in millions) 1 Rice Straw 18.0 2 Wheat Straw 73.5 3 Rice Husk 20.0 4 Coconut Husk 37.5 5 Cotton Stalk 4.4 6 Bagasse 6.0 7 Pine Needles 2.7 8 Non edible grasses 170.0 Natural fibre and crop residues composites in India Due to the light weight, high strength to weight ratio, corrosion resistance and other advantages, natural fibre-based composites are becoming important composite materials in building and civil engineering fields. In case of synthetic fibre based composites, despite the usefulness in service, these are difficult to be recycled after designed service life. However, natural fibre based composites are environment friendly to a large extent. The present requirement of wood in India is about 29 million cubic metres, whereas the estimated production is about 16 million cubic metres only. Apart from wood, natural fibre composites are emerging with an increasing role in building industry to replace timber, steel, aluminium, concrete, etc. Composites are being used for prefabricated, portable and modular buildings as well as for exterior cladding panels. So far, the utilisation of sisal, jute, coir and baggase fibres has found many successful applications. Rice Husk Particle Board Among, all the agricultural residues, the most abundantly available is rice husk. It is the by-product of the most important agro-based industry in the cou