**1. Introduction**

Cashew Nut Shell Oil (CNSO) is a versatile component of the Cashew fruits' nut. The oil which is a dark reddish-brown in colour is resident in a soft honeycomb shell, that is the pericarp of the nut. It is a natural resin that could serve as a valuable raw material for multiple applications. Rapid growth in the world population and increasing standard of living has overstretched petroleum resources as petrochemical feedstock. This among other factors, has culminated in the fast depletion of global petroleum reserves. Therefore, to maintain the standard of living and continuity of industrial sector which is paramount to human survival this decade and beyond, there is a need to find alternative sources of fuel and petrochemical feedstock. Cashew nut shell, a by-product of the cashew industry, is an embodiment of a useful chemical serving as a raw material for the petrochemical industry.

Cashew (*Anacardium Occidentale* L.), a well-known species of the Anacardiceae family [1], is a tropical plant (shrub) found within the region between 23° N and 23° S of the equator. It is a drought resistant tree crop grown successfully in areas with annual rainfall of 50–350 cm. Its height is above 12 m and has a spread of about 25 m. It has an extensive root system which makes it adaptable to a wide range of moisture levels and soil types [2]. On the commercial scale, it is best grown on well-drained, sandy loam soils. Today, it is an economically valuable tree crop in Nigeria, with evergreen leaves, all year round.

The cashew tree consists of the cashew nut fruit (which is a curved edible seed, housed in a honeycomb-like shell), the apple, leaf and bark. The fruit consists of an outer shell, inner shell and the kernel. The thickness of the cashew nut shell is about 1/8 in. (0.32 cm). The soft honeycomb matrix, in between the outer and inner shell, contains a dark brown liquid, which is known as cashew nut shell liquid (CNSL) [3].

The Cashew plant is of great economic significance to Nigeria and other tropical countries due to its valuable products. These products are utilized in food, medicine, chemical and allied industries. In addition to providing shade, the cashew tree is an embellished ornamental plant that suitably controls soil erosion.

Usually, it takes about 3-4 years from planting time before fruiting. Thereafter, the tree can live up to 40 years and more. The cashew fruit (figures 1 and 2) is unusual in comparison with other tree nuts since the nut is outside the fruit. The cashew apple which is about 10 cm long is an edible false fruit, attached to the externally born nut by a stem. Its color ranges from yellow to red, fibrous in nature, very juicy, sweet, pungent and high in vitamins A and C. In its raw state, cashew nut shell (CNS), which is leathery in nature, contains the vesicant oily liquid (CNSL). The shell is separated from the kernel by the testa which is a thin skin sur‐ rounding the kernel.
