Cashewnut shells are the outer covering of the cashew nut, a by-product of cashew processing that holds significant industrial value. The shell contains cashew nut shell liquid (CNSL), a versatile compound rich in phenolic lipids. CNSL is widely used to manufacture friction materials, paints, coatings, brake linings, and resins because of its chemical stability and heat resistance. Unlike edible oils, cashewnut shell oil is primarily a non-edible, industrial product. It plays a vital role in the renewable chemicals sector, offering an alternative to petroleum-based materials.

Cashewnut shells are abundant across cashew-producing countries like India, Vietnam, and parts of Africa, making them a cost-effective raw material. With growing interest in bio-based polymers and green technologies, cashewnut shells are increasingly recognized as a sustainable input. Their use reduces waste from cashew processing while adding value to the supply chain.