Tannins:Tannins are obtained as a by-product from the process of preparing immature betel nuts for masticatory purposes. It was found that tannic acid from the nut, when mixed with ferrous sulphate in warm distilled water gave black writing ink of acceptable quality. He used immature fallen nuts for this purpose. Other uses of tannin are as adhesive in plywood industries and as a textile dye.

Fats:The nuts contain 8-12 per cent fat. Fat from arecanut, can be extracted by solvent extraction using hexane. Areca fat has comparable characteristics with hydrogenated coconut oil. Areca fat can be made edible by refining with an alkali. The fat could be softened by fractional crystallization using hexane (25ºC) and randomization using sodium methoxide, which gave products desirable for use as confectionery fat. Simple blending of areca fat with butter fat and cocoa fat at 3:1 ratio followed by interesterification of areca fat and cocoa fat at 1:1 ratio gave good products acceptable in confectioneries.

Arecanut husk:

It is the outer cover of areca fruit. It constitutes 60-80 per cent of the total volume and weight of the fruits (fresh weight basis). It is now being largely wasted except for being used as an inferior fuel and mulch. Several processes have been developed for utilization of areca husk for making hard boards, plastic and brown wrapping paper. Areca husk is used as a substrate for mushroom cultivation. Arecanut husk fibre is generally longer than woolenised jute, goat hair or coir fibre. About 50 per cent of arecanut husk fibre is finer than other fibres and the remaining 50 per cent of fibre is coarser than those fibres. The tenacity value of arecanut husk fibre is comparable with that of goat hair and woollenised jute. Wet weight of arecanut husk fibre is comparable with that of other fibres. The weight and thickness of all fibre reinforced plastic sheets are comparable. The proportion of fibre in the fibre reinforced plastic sheets varied between 7.6 and 9.9 per cent. The proportion of arecanut husk fibre is higher (9.12 per cent) in comparison with that of glass fibre (7.9 per cent), though the thickness and water swelling ie, increase in weight of the sheets by immersion in water for 20 days, values are same.

Areca leaf sheath:

Leaf sheath is yet another raw material obtained from the arecanut palm. In a year palm sheds 5-6 leaves. A process has been developed for making plyboards from areca leaf sheath. These boards can be used for making suitcases, fileboards, and tea chests. Leaf sheath cup making machine is available in the market for making arecanut leaf sheath cups of different sizes and shape.

Arecanut leaf sheath was found suitable for making plyboards. Two plies of processed arecanut leaf sheaths in combination with an ordinary wood veneer as core glued with urea formaldehyde resin are used for making the plyboards. Leaf sheaths obtained from the farm are highly heterogenous having variations in structure, shape and thickness. The rear end is thicker and the two edges are thinner. The thickness at the center ranges from 3.0 – 8.5 mm (average 5.0 mm). A comparatively homogenous piece of fairly uniform thickness and size 50-65 x 20-25 cm can be obtained if a piece of about 10 cm length from either sides along the grain direction, 5 cm from the distal and 10-15 cm from the end across the grain direction are trimmed out from the sheath. Further, to get a flat sheath of uniform thickness and to remove the buck lings of folds, the sheath is flattened under pressure and heat. For this, the sheaths are soaked in water to about 75 per cent moisture and then pressed for 30 min in a hot Plate press at 4 kg/cm2 pressure and 110ºC temperature. This process gives flat sheaths of 1.0-1.5 mm thickness with about 12 per cent moisture. To prevent fungal growth on the sheath surface, it can be soaked in 1 per cent copper sulphate solution for 24 hr before pressing. The pressed sheaths are then air dried for one hour or longer. The arecanut leaf sheath plyboards made with two veneers of areca sheaths as the faces and one veneer of even an ordinary wood species like Mango as core ply and bonded with Urea formaldehyde resin make commercially acceptable boards with average dry and wet glue shear strengths of 50 kg and 12 kg respectively.

Arecanut stem and leaf:

Arecanut stem forms a useful building material in the villages and is widely used in arecanut growing area for a variety of construction purposes. The leaves are good source of organic manure. Their approximate composition is N2 (0.94 per cent); P2O5 (0.096 per cent) and K20 (1.00 per cent).

Utilisation of waste of arecanut plantation for mushroom production

In India, the cultivation of mushrooms is limited to three species viz., white button mushroom, paddy straw mushroom and oyster mushroom. Oyster mushrooms are the ideal ones for the arecanut sector due to its ability to utilize lignin rich arecanut wastes and the climatic conditions prevailing in plantations are also ideal for its growth. Oyster mushrooms, known as wood fungi, are endowed with ligninolytic and cellulolytic properties to utilize a wide range of agricultural residues as substrates for growth and fruit body production. Paddy straw is the most widely used substrate for its cultivation. But its increasing cost and decreasing availability are factors, which prompted research workers to look for alternate substrates for oyster mushroom cultivation. Conditions have been standardized for cultivation of oyster mushrooms using arecanut leaf sheath and bunch waste. The steps in oyster mushrooms cultivation include development of spawn, substrate preparation, spawning, incubation for spawn running and opening and maintenance of beds for cropping.

Spawn, the vegetative seed of the fungus, can be obtained either from research institutions or can be prepared with adequate training. An efficient and stable strain of Pleurotus isolated from sporocarps should be used for spawn preparation using grains such as wheat, sorghum, maize, jowar or paddy straw as substrates. Pasteurization of substrates is necessary to avoid contamination and to obtain higher yield. Steam sterilization, hot water treatment and chemical sterilization are the effective methods. Steam sterilization at 1.02 kg/cm2 pressure in an autoclave for one hour is an efficient method of sterilization. Hot water dip of the substrate at 80°C for 60-120 minutes is another method, which can be easily adopted. Chemical sterilization method involves treatment with formalin and bavistin in substrate soaking water for 18 hours. Arecanut bunch waste and leafstalk are pasteurized by soaking in a solution of 500 ppm formalin + 25 ppm bavistin.

Polyethylene bag method is the commonly followed method of cultivation. Polyethylene bags (150-200 gauge) of 66 x 45 cm size are punched to facilitate cross ventilation. Spawning is done by multilayered technique using 3 per cent spawn. For spawn running and cropping, the filled up bags are incubated in cool dark place. In 15 to 20 days white thread like mycelium covers the entire substrate and the whole mass turns into a solid cylindrical structure. At this stage the polyethylene bags are ripped open and incubated for cropping by hanging or by stacking on the shelves of mushroom house with watering daily twice after two days of opening of beds.

Low cost mushroom sheds can be built with coconut/areca stem and plaited coconut leaves inside arecanut plantations. Multilayer rack can be prepared with coconut/ areca stem inside the shed to keep the spawned substrate for spawn running and cropping. Ventilators with insect proof nets are to be provided on all sides of the shed. Mushroom production is 69 per cent and 49.8 per cent in a cropping period of 47 to 52 days in arecanut bunch waste and leaf sheath, respectively.