The mighty cashew

Abstract

The generic name ‘cashew’ applies to a tree, its fruit, its nuts, and the family to which it belongs. The tree has been cultivated in tropical countries for close on five hundred years, and from the fruit to the nut to the shell, the cashew is basically edible and useful. Outside the Tropics the tree is perhaps best known for its edible nuts. However of the various natural products of the cashew, it is the caustic, black phenolic oil known as cashew nut shell liquid (CNSL), until recently routinely discarded as a waste product, which has been found to be of most interest, as it can be used in numerous industrial and engineering applications. CNSL is essentially a mixture of phenolics and is a good natural alternative to petrochemically derived phenol. Furthermore CNSL has found uses in areas as diverse as paints, corrosion resistant varnishes, and natural composite materials. The fact that CNSL is also a low cost renewable resource which until recently was thought of as a waste product only adds to its appeal and suggests that an exciting future awaits this fascinating material.