<p>Mr Omprakash N. Phadnis, M/S. N.S. Phadnis, Tamil Nadu has wriiten an article on Cashew Nut Shell Liquid and its types to be publish in the Cashew Week as a special coverage.</p> <p>Cashew Nut Shell Liquid (CNSL) is used in India for ages now. Since the Portuguese brought this crop to India, it showed its presence more on west coast than on south. For decades only Kerala, Karnataka and Goa were good cultivators and it took some years for Tamil Nadu and AP to join them. Today, Gujarat, Orissa, West Bengal and some parts of Manipur are also cultivating.</p> <p>Lot of talks is always on for Cashew Nut Shell Liquid (CNSL) prices, availability etc. We always consider only one type of CNSL in our mind. Let us discuss types of CNSL here.</p> <p><strong>Cold Pressed CNSL</strong>: This is the CNSL presently used worldwide. This is extracted from raw cashew shells by expelling CNSL by crushing the CNSL in an ordinary ground nut expeller. These expellers are of various types. The crusher exerts pressure on the shell and the shells get crushed and oil is out. This oil while coming out brings lot of particles of the honeycomb structure along with and therefore, contains moisture, ash, foreign materials etc. Therefore, the oil is properly dehydrated and then settled so that the moisture is removed as well as the ash and foreign matters settle. Properly dehydrated oil with settling of more than 72 hours satisfies ISI 840 amended properly.</p> <p><strong>Hot type CNSL</strong>:</p> <p>· Prior to 1995, the hot type CNSL was available more in Panruti and Kerala pockets. Generally, a kiln was used as chamber and heat was applied externally. The temperature used to be around 200 degree and above and oil used to ooze out from cashew shells. It was getting collected. The oil was dark colored (dark brown) with higher viscosity and lower iodine value. This oil contained about 12% moisture etc and decarboxylation or acid treatment was done over the oil to get it to standard quality of ISI 840 specification. This oil was used more for brake lining industry. Even today such kilns are existing in Panruti area.</p> <p>· About fifty years back, method of batch oil extraction was used for cashew shelling. In this nuts were immersed in hot CNSL. The nuts were getting cracked and the CNSL in the shells of the nut used to get added up to outside basket of CNSL. This oil is probably the best CNSL available so far, which was having low acid value, good color and all ISI 840 properties. Unfortunately, the kernels used to become ivory in color. Moreover running cost of the plant was too much and therefore, this process was totally eliminated. This process mainly existed in Kerala.</p> <p><strong>Solvent Extracted CNSL</strong>: All are aware of this process of extraction which is used for rice bran oil or groundnut oil etc. For cashew shells, they are cut or disintegrated and then digested with solvent. Petroleum solvent like n-hexane is used for the purpose. Here entire quantity of CNSL gets dissolved in the solvent and this solution is filtered to remove impurities. This solution is subjected to distillation. The solvent is recollected and the pure CNSL is obtained after driving off the solvent from it. This CNSL is the purest and has got better properties. Due to very high cost of solvent and therefore high extraction cost, the process is not used in India. It would work out today, if the solvent is made available around Rs. 30.00 per liter. In this process the yield of the oil is most but the cake is practically without oil and therefore has no use for firing. But the cake could be used for various other purposes.</p>