Sustainable Pistachio Dehulling Waste Management and Its Valorization Approaches: A Review

Abstract

Purpose of Review: In countries such the USA, Iran, and Turkey, pistachio nut is considered one of the most economically valuable agricultural products. Pistachio production and related dehulling processes generate a large quantity of organic waste, containing green hull, cluster woody part, shells, and leaves. The inadequate conventional management of such wastes calls for sustainable and economical strategies not only to enhance resource efficiency but also to create value. Recent Findings: Pistachio residues have a high content of total extractives and essential oils and a considerable amount of phenolic compounds that explain their good antioxidant activities and other potential human health benefits. Furthermore, considering the generation volume (about 660,000 tons) and lignocellulosic structure, pistachio residues can also be sustainably used to produce value-added products, such as biofuels, phytochemicals, activated carbon, and other potential bioproducts such as filamentous fungi as protein enriched biomass, single-cell protein (SCP), and volatile fatty acids. In general, recent studies have not comprehensively investigated all value-added potential products. Summary: This review provides a thourough insight into the present pistachio processing industries, and pistachio waste chemical composition and characteristics. Furthermore, the applications of pistachio residues as a renewable source for the production of potential value-added products by various thermochemical (pyrolysis, gasification, and liquefaction), physicochemical (solvent extraction, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and extraction by pressurized liquids (PLE)), and biological (anaerobic digestion (AD) and fermentation (solid-state and submerged)) processes are presented including an analysis of the advantages and disadvantages of such methods. In this regard, production of new products such as edible filamentous fungi and antioxidant, and their market appeal has been briefly considered.