Advances in extraction and sustainable utilization of cashew nut shell liquid (CNSL) for industrial applications

Abstract Cashew nutshell liquid (CNSL), a highly versatile byproduct of the cashew processing industry, offers remarkable potential across a broad spectrum of industrial and chemical applications. Extracted from the soft, spongy honeycomb structure inside the hard outer shell of the cashew nut, this dark reddish-brown, viscous liquid is a rich, renewable source of unsaturated phenolic compounds. Among bio-based raw materials, CNSL stands out for its cost-effectiveness, high chemical reactivity, and wide applicability in the production of polymers, coatings, resins, and biofuels. This review presents a comprehensive analysis of various extraction techniques used to isolate CNSL, with a particular focus on chemical extraction methods. Three primary extraction approaches – thermal, mechanical, and chemical – are discussed, each uniquely influencing the yield and composition of the extracted CNSL. Special attention is given to chemical extraction methods such as solvent extraction, Soxhlet extraction, and supercritical carbon dioxide (SC–CO 2 ) extraction, evaluating their efficiency, selectivity, and scalability. He extracted CNSL typically contains four major constituents: anacardic acid, cardanol, cardol, and 2-methyl cardol, with their relative proportions depending heavily on the extraction technique and operational conditions. Beyond traditional methods, this review also highlights recent advancements in green chemical processes aimed at reducing environmental impacts while enhancing material performance. These innovations pave the way for sustainable production of industrial chemicals and biomaterials from cashew waste, supporting global initiatives toward a circular economy and the principles of green chemistry.